Astronomy 3130/5110

Observatory Handbook

University of Virginia

2011

Contents

1 The McCormick and Fan Mountain Observatories 11. The Leander McCormick Observatory . . . . . . . . . . . . . . . . . . . . . . 32. The Fan Mountain Observatory . . . . . . . . . . . . . . . . . . . . . . . . . 43. Public Night at the McCormick and Fan Mountain Observatories . . . . . . 54. Department of Astronomy, University of Virginia . . . . . . . . . . . . . . . 5

2 The Observatory Calendar and Schedule 71. General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92. Reserving an Observatory . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93. Changing or Deleting the Reservations . . . . . . . . . . . . . . . . . . . . . 10

3 Loss and Breakage, Key, and Safety Agreements 11

4 The Doghouse Observatory 6-inch Clark Refractor 171. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192. Operation of the 6-inch Clark Refractor . . . . . . . . . . . . . . . . . . . . . 193. Finding Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214. Closing Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4.1. Stow the 6-inch Clark refractor . . . . . . . . . . . . . . . . . . . . . 244.2. Secure the doghouse . . . . . . . . . . . . . . . . . . . . . . . . . . . 244.3. Observer’s Room (Room 106) . . . . . . . . . . . . . . . . . . . . . . 244.4. Secure the Observatory and Grounds: . . . . . . . . . . . . . . . . . . 25

5 The Doghouse Observatory 10-inch Meade LX200 Schmidt-Cassegrain 271. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292. Operation of the 10-Inch Meade Telescope . . . . . . . . . . . . . . . . . . . 293. Closing Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.1. Stow the 10-inch Meade . . . . . . . . . . . . . . . . . . . . . . . . . 323.2. Secure the doghouse . . . . . . . . . . . . . . . . . . . . . . . . . . . 323.3. Observer’s Room (Room 106) . . . . . . . . . . . . . . . . . . . . . . 323.4. Secure the Observatory and Grounds: . . . . . . . . . . . . . . . . . . 32

6 The McCormick Observatory 26-inch Clark Refractor 351. A Tour of the Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382. Opening Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403. Locating an Object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434. Telescope Tailpiece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

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5. Visual Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476. Basic CCD Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 487. Warnings and Additional Instructions . . . . . . . . . . . . . . . . . . . . . . 498. Closing Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509. Opening Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5310. Closing Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

7 The Fan Mountain Observatory 40-inch Astrometric Reflector 551. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583. Startup Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584. Initializing the Coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . 615. Shutdown Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616. The Filter Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 627. The Telescope AutoGuider . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

7.1. Setup Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667.2. Internal Filter Wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . 667.3. Image Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667.4. Focus and Finding Procedure . . . . . . . . . . . . . . . . . . . . . . 667.5. Calibrate Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . 677.6. Track Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 677.7. Monitor Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 677.8. Many More Features . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

8 The Fan Mountain Observatory 31-inch Tinsley Reflector 691. General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 712. Care of the Telescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 733. Opening Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 734. The Control Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745. Closing Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766. The Control Paddle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 777. The Guide Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 788. Alcove and Circuit Breakers . . . . . . . . . . . . . . . . . . . . . . . . . . . 799. Equipment used with 31-inch telescope . . . . . . . . . . . . . . . . . . . . . 8010. Log Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

9 The Fan Mountain Observatory 10-inch Astrograph 831. General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 852. Opening procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 853. Telescope Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854. Closing Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

10 The GenI CCD Camera (Imaging) 871. System Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 892. CCD Camera Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . 893. The Dewar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

3.1. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 913.2. Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

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3.3. Potential Problems and the Dewar Vacuum . . . . . . . . . . . . . . 924. Operating the CCD Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

4.1. Login . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 934.2. Starting IRAF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 944.3. Starting the Voodoo Program . . . . . . . . . . . . . . . . . . . . . . 944.4. Filter Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . 994.5. Scope Control System . . . . . . . . . . . . . . . . . . . . . . . . . . 1004.6. Taking an Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . 1024.7. Ending a CCD Session . . . . . . . . . . . . . . . . . . . . . . . . . . 102

11 The GenII CCD Camera (Spectroscopy) 1031. System Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1052. CCD Camera Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . 1053. The Dewar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

3.1. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1073.2. Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1073.3. Potential Problems and the Dewar Vacuum . . . . . . . . . . . . . . 108

4. Operating the CCD Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . 1094.1. Login . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1094.2. Starting IRAF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1104.3. Starting the Voodoo Program . . . . . . . . . . . . . . . . . . . . . . 1104.4. Scope Control System . . . . . . . . . . . . . . . . . . . . . . . . . . 1164.5. Taking an Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . 1174.6. Ending a CCD Session . . . . . . . . . . . . . . . . . . . . . . . . . . 117

12 The Fan Observatory Bench Optical Spectrograph (FOBOS) 1191. Instrument Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

1.1. The Focal Plane Module . . . . . . . . . . . . . . . . . . . . . . . . . 1221.2. The Fiber Train . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1241.3. The Bench Spectrograph . . . . . . . . . . . . . . . . . . . . . . . . . 124

2. Available Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1263. Setting Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

3.1. Filling the Dewar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1283.2. Enabling the Vibration Isolator . . . . . . . . . . . . . . . . . . . . . 1283.3. Preparing the Spectrograph Room . . . . . . . . . . . . . . . . . . . 1293.4. Computer Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1293.5. Preparing the Dome Room . . . . . . . . . . . . . . . . . . . . . . . . 1303.6. Please please please... . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

4. Observing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1314.1. What Data Should You Collect? . . . . . . . . . . . . . . . . . . . . . 1314.2. Spectrograph Control System . . . . . . . . . . . . . . . . . . . . . . 1334.3. Software Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . 1334.4. Calibration Lamp Exposures . . . . . . . . . . . . . . . . . . . . . . . 1344.5. Telescope Coordinate Initialization . . . . . . . . . . . . . . . . . . . 1354.6. Focal Plane Module Focus . . . . . . . . . . . . . . . . . . . . . . . . 1364.7. Coarse Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1364.8. Fine Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

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4.9. Guiding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1374.10. Throughput and Exposure times . . . . . . . . . . . . . . . . . . . . 138

5. Shutting Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395.1. Disabling the Vibration Isolator . . . . . . . . . . . . . . . . . . . . . 1395.2. Spectrograph Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395.3. Dome Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395.4. Control Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

6. Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1407. Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1418. Neon/Argon/Xenon Spectral Line Identification Charts . . . . . . . . . . . . 143

13 The Santa Barbara Instruments ST-8/ST-1001E CCD Cameras 1471. CCD Set Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1502. CCD Operation with CCDOPS . . . . . . . . . . . . . . . . . . . . . . . . . 151

14 The OptoMechanics Model 10C Spectrograph 1551. General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1572. Use of the Spectrograph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

2.1. Instrument Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1572.2. Spectrograph Set Up . . . . . . . . . . . . . . . . . . . . . . . . . . . 1612.3. Spectrograph Operation . . . . . . . . . . . . . . . . . . . . . . . . . 1632.4. Slit and Grating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1632.5. Camera Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1632.6. Spectral Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1632.7. Focusing the Spectrograph . . . . . . . . . . . . . . . . . . . . . . . . 1652.8. Observing with the Spectrograph . . . . . . . . . . . . . . . . . . . . 166

3. Reduction of Spectrographic Data . . . . . . . . . . . . . . . . . . . . . . . . 1673.1. Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1673.2. MaxIM DL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1683.3. MIRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

4. Ne–Hg/Ar Comparison Sources . . . . . . . . . . . . . . . . . . . . . . . . . 1695. Central Wavelength vs. Grating Tilt . . . . . . . . . . . . . . . . . . . . . . 1706. References on CCD Imaging and Spectroscopy . . . . . . . . . . . . . . . . . 1717. File Transfer to UNIX Workstations . . . . . . . . . . . . . . . . . . . . . . . 1718. Reduction of Spectrographic Data with IRAF . . . . . . . . . . . . . . . . . 172

8.1. Viewing and Extracting Spectra . . . . . . . . . . . . . . . . . . . . . 1728.2. Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1728.3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1748.4. Extracting the Comparison Spectrum . . . . . . . . . . . . . . . . . . 1768.5. Wavelength Calibration . . . . . . . . . . . . . . . . . . . . . . . . . 177

15 The Astrovid 2000 Video Camera 1811. General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1832. Setting Up the Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

2.1. Mounting the Camera . . . . . . . . . . . . . . . . . . . . . . . . . . 1842.2. Connecting the control box and power supply . . . . . . . . . . . . . 1852.3. Adjusting the Focus . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

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3. Setting Up a Video Output Device . . . . . . . . . . . . . . . . . . . . . . . 1864. Camera Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1875. Centering the Image on the CCD . . . . . . . . . . . . . . . . . . . . . . . . 1876. Capturing Images With the McCormick Laptop PC . . . . . . . . . . . . . . 1887. Shutting Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

16 The Astronomy Library and Astronomical Literature 1911. The Astronomy Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

1.1. Reference and Information Services . . . . . . . . . . . . . . . . . . . 1932. Guide to Astronomical Literature . . . . . . . . . . . . . . . . . . . . . . . . 194

2.1. General Guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1942.2. The Age of the Computer . . . . . . . . . . . . . . . . . . . . . . . . 1942.3. Periodicals/Journals . . . . . . . . . . . . . . . . . . . . . . . . . . . 1952.4. Conference Proceedings . . . . . . . . . . . . . . . . . . . . . . . . . 1962.5. Observatory Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . 1962.6. Review Literature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1972.7. Abstracts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1972.8. Almanacs, Data Books, Handbooks . . . . . . . . . . . . . . . . . . . 1972.9. Charts and Atlases . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1982.10. Catalogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1992.11. Publisher’s Series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1992.12. Observational Astronomy . . . . . . . . . . . . . . . . . . . . . . . . 2002.13. Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2012.14. Specific References Related to Observational Astronomy . . . . . . . 201

A Using IRAF on a UNIX Workstation 2051. Starting IRAF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2072. FITS vs. IRAF format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2073. Common IRAF Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2094. Image Reduction in IRAF . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

4.1. Procedural Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 2124.2. The CCDRED Package . . . . . . . . . . . . . . . . . . . . . . . . . . 2124.3. CCDLIST—What do I got? . . . . . . . . . . . . . . . . . . . . . . . 2144.4. Test Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2154.5. The Log File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2164.6. Trimming the Image and Correcting the Overscan . . . . . . . . . . . 2164.7. Bias Combining and Subtracting . . . . . . . . . . . . . . . . . . . . 2184.8. Dark Combining and Subtraction . . . . . . . . . . . . . . . . . . . . 2214.9. Flat-Fielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2214.10. Illumination Correction . . . . . . . . . . . . . . . . . . . . . . . . . . 222

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Chapter 1

The McCormick and Fan MountainObservatories

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McCormick and Fan Mountain Observatories(Rev. August 09, 2011)

1. The Leander McCormick Observatory

The Leander McCormick Observatory is located on Mount Jefferson at the edge of theUniversity of Virginia Grounds. It is found at latitude 38◦02′00′′ and longitude 78◦31′24′′.The observatory is 866 ft (264 m) above sea level.

This observatory has three telescopes which are described briefly below. Other details aregiven in this handbook.

1. 26-inch Clark refractor: The 26-inch telescope has a 26-inch diameter lens witha focal length of 32.5 ft (9.9 m). Its field of view is about 0.75 of a degreewith photographic plates. This telescope has been used primarily for astrometricobservations and the observatory plate file contains over 140,000 plates which weretaken between 1914 and 1995 for the purpose of determining stellar motions anddistances.

2. 6-inch Clark refractor: The 6-inch telescope is an Alvan Clark refractor with a focallength of 1.83m. It is housed in a small roll-off roof observatory (the Doghouse) on thegrounds of McCormick Observatory next to the 26-inch dome.

3. 10-inch Meade: The 10-inch telescope is a Meade LX200 Schmidt-Cassegraintelescope with a focal length of 2.5m. It is housed in the Doghouse next to the 26-inchdome.

4. Observatory Building: This building contains a small museum, lecture room,observer’s room, plate vault, restroom, and other support facilities for the observatory.

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2. The Fan Mountain Observatory

The Fan Mountain Observatory is on Mount Oliver in the Fan Mountains; latitude 37◦52′41′′,longitude 78◦41′34′′. Fan Mt. is 1825 feet (556 m) above sea level and 1200 feet above thesurrounding terrain. The observatory is located near Covesville, VA about 16 miles southof Charlottesville. The turn-off from Rt. 29 is about 13.5 miles south of I 64. From Rt. 29there is a 3.5 mile gravel road to the top. See map. Please exercise care when crossing therailroad tracks as the line is often used by fast moving freight trains and there is no signal.Always come to a complete stop before crossing the tracks. The road to the Observatory isnarrow and winding and to avoid traffic jams on the Fan Mountain Public Night, the roadwill be up only from 7:15–9:00 p.m., and down after 9:15 p.m. only.

Warm clothing should be worn for trips to Fan Mt. since it may be much colder and windieron the Mountain than in town and you will be outside (or in the dome) much of the time.

Fan Mountain Observatory has three telescopes which are described briefly below. Otherdetails are given in this handbook.

1. 40-inch astrometric reflector: The 40-inch telescope has a 43-inch diameter primarymirror, a 20-inch diameter secondary mirror, and a 40-inch diameter corrector lens toprovide a stable, large-field telescope for precise measurements of the motions anddistances of nearby stars. It has also been used for studies of galaxies and quasars. Itsfield of view is about 0.67 of a degree (somewhat larger than the full moon) with 10-inch photographic plates. The field of view using the SITe 2048 CCD is approximately12.5 arcmin on a side. It is also equipped with a fiber-fed low resolution spectrographsystem, used to study the motions and metal abundances of giant stars in the Galactichalo.

2. 31-inch Tinsley reflector: The 31-inch telescope is a standard Cassegrain reflectorwith a 31-inch primary mirror and an 8.5-inch secondary mirror. It is primarily usedfor near infra-red astronomy..

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3. 10-inch astrograph: The astrograph is a wide-field camera for photographing largesections of the sky at one time. Over 900 red-dwarf stars have been discovered withthis instrument.

4. Station House: This building contains a darkroom, mechanical shop, restrooms,living quarters, and other support facilities for the Observatory.

3. Public Night at the McCormick and Fan Mountain Observatories

McCormick Observatory is open to the public the first and third Friday of each month. Notickets or reservations are necessary. Groups must make special arrangements. Twice a yearthere is a public night at Fan Mountain, once in April, and again in October. Tickets (whichare free) are required for the Fan Mountain Public Night. Call 924-7494 for details.

4. Department of Astronomy, University of Virginia

The McCormick and Fan Mountain Observatories are operated by the faculty and staff ofthe Department of Astronomy at the University of Virginia. For general information aboutthe Astronomy Department, you may consult the World Wide Web URL address of thedepartment’s home page: http://www.astro.virginia.edu.

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Figure 1. Directions to Fan Mountain

Figure 2. Layout of Fan Mountain Observatory

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Chapter 2

The Observatory Calendar andSchedule

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The Observatory Calendar and Schedule(Rev. August 09, 2011)

1. General Information

Both the McCormick and Fan Mountain observatories are now reserved throughan online web calendar. The Calendars are used to schedule events and observ-ing runs. There is a calendar for each of the observatories which is found at:http://www.astro.virginia.edu/research/observatories/calendar/

Authorized users may reserve time at either McCormick or Fan Mountain. See RickyPatterson or the webmaster for information on how to reserve either observatory

To browse the calendar, use the McCormick Calendar and the Fan Mountain Calendar links.To reserve the observatory, use the Reserve Observatory link.

2. Reserving an Observatory

Before reserving an observatory (referred to as Adding an event on the observatories calendarpage), you should make sure that the observatory is available during the times you intendto use it. This can be checked easily by using the list view option on the calendar page forthe specific observatory.

You need to login to be able to reserve any of the observatories. Contact the course TA toknow your group’s login id and the password. You can change your password at any timeon the login page.

Once logged into the calendar, choose the link add event. At the following page, you needto fill in the following fields:

• Start Date: The date of the observation.

• End Date: The date when you finish the observation. Note that if you intend toobserve till or past midnight, this date is the next day’s date.

• Start Time

• End Time: Note: midnight is 12:00 AM.

• Telescope Use: Enter the details of the telescopes and the equipment you will beusing for the observing run.

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• Category: Use ASTR3130 or ASTR5110 as the category. Enter your group numberand the name of the TA.

After filling in all the above fields, use the Submit event link to reserve the observatory. Ifthere is a problem with the form, it will take you to a page showing the problem. Correctthat and submit the page again.

Once you submit an event correctly, it will show you the details of the event added. Makesure the information there is correct. If not, use the Edit this event button to change theevent and submit it again.

3. Changing or Deleting the Reservations

If you later want to cancel or update your reservation, you need to login into the calendaragain and first find that event using the search events link. At this page you can limit yoursearches by different criteria, such as the start and end dates, instrument use, etc. One ofthe most useful limiting criterion for you would be to search within your events (use thecheck-box corresponding to My events), which will display only your events. Once you findyour event, use the Edit event link to either update or delete the event.

Note: Do NOT reserve the observatories for times/days you don’t need. The telescopesare heavily used and you should give others (including your fellow ASTR3130 or ASTR5110students) equitable chance for observing.

The following applies to ASTR 3130 students only:

To insure that a single group does not take up all the observatory time, the following policywill be followed:

The observatories calendar will not let any group sign-up for more than twohours of observatory time each night. A group can, however sign up for morehours for a particular night under the following circumstances:

• More time is available (check at the observatory calendar)

• You are signing up less than 24 hours in advance (this allows every groupreasonable opportunity to plan ahead and reserve time).

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Chapter 3

Loss and Breakage, Key, and SafetyAgreements

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Loss & Breakage, Key and Safety Agreements(Rev. August 06, 2007)

Loss and Breakage Agreement

The equipment you will use in this course is fragile, expensive and very difficult to replace.In order that everyone has equal opportunity to complete the course requirements andresponsibility can be assigned fairly we have implemented the following loss and breakageagreement.

1. You are on your honor to report all damage to the instructor or TA immediately. Donot attempt to fix it yourself. Shut down the equipment and report the problem.If the nature of the damage endangers other equipment (roof won’t close, electricalproblems) you must contact us. If neither the instructor nor the TA can be reached,contact any astronomy department member.

2. A written description of any damage or problem is to be given to the instructor thefollowing day. In order for observing equipment to be repaired promptly, we must knowspecifics about the problem. Damage caused by the student will be assessed againstyou.

3. In the case of loss or damage which cannot be assigned as the responsibility of agiven individual, all students authorized to use the equipment during the time periodin which the problem occurred will share equally the cost of replacement or repair.Checks on the equipment will be made daily and the last users will be held responsiblefor its condition. If an item appears damaged or is missing when you first check it out,notify your instructor in writing and the previous users will be assessed damages.

4. Always fill out the observing log for every observing session. No credit willbe given for observations carried out during an unlogged session!!!

5. In all cases the judgment of the Astronomy Department in assessing the damage costsis final. We will make every effort to be fair subject to the constraint that the costsmust be paid. Normal wear will be allowed for.

6. All assessed costs must be paid within 4 weeks of notification. Your grade will bewithheld until all payments have been made.

Key Agreement

For completion of the requirements of this course you will be issued one or more keys whichyou must return at the end of the semester. Any keys signed out over night should bereturned promptly the next weekday morning.

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Your grade will be withheld until all keys are returned to the department. Thesekeys are loaned to you for use in completing the requirements of this course. They are notto be copied, loaned to friends, or used to gain access to the department’s facilities for anynon astronomy related purpose. You may not bring friends with you to the observatories.

Safety Agreement

This is a laboratory course and like any lab course there are potential hazards which couldresult in injury. For the most part you will be working in the dark either outdoors conductingobservations or in the darkroom. Use common sense when moving about; do not make anysudden, quick movements. Telescopes have sharp corners and parts that stick out. Make amental note of the locations of all equipment, including steps or ladders. This informationmay help you to prevent accidents. In any event, always carry a flashlight. Remember thatyou are more likely to hurt yourself than large pieces of equipment.

McCormick Observatory Much of your observational work will be done here using the6-inch and 10-inch telescopes in the Doghouse and the 26-inch in the main dome.

Some safety notes:

1. The photometer has a high voltage power supply and all the telescopes have electricalconnections. Be alert.

2. No horseplay. No alcoholic beverages. No smoking.

3. Watch your footing in the Doghouse.

4. First-Aid equipment is located in the built-in bookshelves in the Observers Room.There are several phones in the building. Note their locations. In case of an emergency,you must dial a “9” before 911: 9-911.

Fan Mountain Any trips to the Fan Mountain Observatory will be supervised by the TAor faculty. It is always about 10 degrees colder at Fan, so you will need to dress warmly.

Injuries If an injury of any kind occurs, notify the instructor if he or she is present. If theinjury is minor and no supervisor is present, you should notify the instructors the next day.If the injury appears even remotely serious call the rescue squad (911). Notify the instructorimmediately. (Call her/him at home if necessary.) Emergency numbers are posted by thephone.

Wear suitable clothing at all times. Remember than even 60 degree weather can be chillingif you are engaged in observing with a minimum of movement.

Metal surfaces get very cold; numbed hands can lead to accidents. Walk slowly and carefullywhen leaving a lighted room and entering the dark. It takes a minimum of 5 minutes foryour eyes to adjust to darkness and more than a half hour for full adaptation. Once youreyes are night adapted, it is best to keep them that way until all observations are completed.Repeated switching from light to dark will cause eye strain.

After reading these agreements, sign the pledge.

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OBSERVATIONAL ASTRONOMY

Sign and return this sheet to the instructor of this course.

LOSS AND BREAKAGE AGREEMENT

I understand the loss and damage policy described elsewhere and agree to promptly payreplacement or repair charges assessed me by the Astronomy Department. I will report allproblems in the manner prescribed as quickly as possible.

Name:

SAFETY AGREEMENT

I understand the policy regarding safety for this course and will act responsibly to preventaccidents.

Name:

KEY AGREEMENT

On my honor as a student I agree to return those keys loaned to me upon completion of thecourse. I will not duplicate any key nor will I loan a key to anyone under any circumstances.

Name:

ID#: Date:

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16

Chapter 4

The Doghouse Observatory 6-inchClark Refractor

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6-inch Clark Refractor(Rev. August 09, 2011)

1. Introduction

The 6-inch Clark refractor is housed in the Doghouse at the McCormick Observatory. Ithas an equatorial mount and is equipped with a Saegmuller weight-driven mechanical clockdrive. It is a simple and reliable telescope to use if the proper care is exercised. It is also anirreplaceable piece of equipment; treating it with care will allow it to be used for many, manyyears to come. The Doghouse telescopes should not be used until you have been shown howto use these telescopes and have been given permission by a TA or faculty member to usethem on your own (i.e., checked out).

2. Operation of the 6-inch Clark Refractor

Roof: The roll-off roof is operated manually with the winch beside the door. There is a viceclamp holding the chain in place which must be loosened before opening the roof. Be sureto reclamp the chain TIGHTLY after closing up for the night. Never move the roofunless both telescopes are horizontal and clear of its path.

Lens caps: Carefully remove lens caps on both the 6-inch lens (1, see Figures) and finder(4) after opening the roof. Always replace them before closing. Be aware that they have atendency to bind.

Clock Drive: Start and stop the clock drive with the push-pull control (6) on the northside of the pier on the outside of the clock mechanism cover. Open the glass door on thewest side of the pier and you will find the winding shaft (7), for the crank. The crank is

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kept on the shelf with the eyepiece box. Open the access door on the south side of the pierso you can watch the pulley and weight. Slide the crank sleeve over the shaft and slowlywind the weight up until the top of the weight is level with the bottom of the access hatch inthe hollow pier. Never overwind the drive; this will damage the drive mechanism.You will have to rewind it every 45 minutes or so. If the drive is operating properly, thegovernor (5) inside the door will spin rapidly. Always turn the drive off before leavingthe building.

Finder: A low-power, wide-field finder telescope (4) is mounted piggyback on the 6-inch. Itcontains cross-hairs which are somewhat difficult to see against a dark sky. The alignmentbetween the two telescopes may not be perfect—i.e., an object centered on the cross-hairsmay not be in the center of the main telescope field, so always start with the lowest powereyepiece. The focus may need to be adjusted. Do this by carefully moving the draw tubeeither in or out. However, be careful not to knock the finder out of alignment while doingthis.

Controls: Apart from the clock drive there are only 5 controls. The clamps and slow motioncontrols (8), are located at the ends of the long shafts extending back toward the eyepieceend of the telescope. The two outer knobs control RA slow motion and clamp, and the innerones have the same functions in DEC. The focus is on the side of the eyepiece mountingtube.

Clamps: The clamps are the larger pair of barrel shaped knobs. If turned counter-clockwise,they completely free the Right Ascension (RA) and Declination (DEC) motions for pointingthe telescope. When the desired object has been located, carefully clamp first one thenthe other, by turning the knobs clockwise. These only need to be firm not tight. Do notover-tighten them, as they become difficult to undo and may damage the gears. Clampingthe RA engages the clock drive, if it is “on”, and causes the telescope to track the objectacross the sky. Do not attempt to move the telescope without making sure theappropriate motion is unclamped.

Slow motion: The slow motions are the flatter, disk-like knobs, again one for each motion.Turning these knobs adjusts the pointing of the telescope in either RA or DEC for centeringobjects in the eyepiece field, correcting the drive motion, etc. The telescope must be clampedin that motion, in order for these to function. The DEC slow motion moves the telescopeon a tangent arm which has limited travel. Be sure that the tangent arm is in the middle ofits travel range, before you begin observing.

Focus: Use the focus knob on the side of the eyepiece mount to adjust the eyepiece focus.After changing eyepieces the image may need refocusing. It is difficult or impossible to focuson faint or diffuse objects, so use a bright, naked-eye star before trying to find such an objector use a nearby field star. Occasionally you will have to adjust the sliding draw tubes to finda focus. A diagonal prism is provided to allow easier viewing through the eyepiece.

Setting Circles: The setting circles (2) are the large white wheels marked with coordinates;one in DEC and one in Hour Angle (HA). The HA wheel is marked from 0 - 24 hours in romannumerals, and measures the time since the last meridian crossing. Therefore, depending onthe telescope orientation, 0 hour angle (i.e. the meridian position) will correspond to either

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Figure 1. 6-inch Alvin Clark Refractor. (1) Objective Lens, (2) Setting Circles,(4) Finder, (8) Slow Motions and Clamps, (9) Eyepiece.

0 hours or 12 hours. Larger numbers are toward the west. E.g. an Hour Angle of 31

2hours

east would be found at XX1

2on one side of the pier and VIII1

2on the other. A little care

and practice will prevent confusion.

The coordinates on the painted wheel surfaces are reasonably accurate for declination. ForHA, it is best to use those inscribed in brass on the edge of the wheel. These must be readwith the mounted magnifiers (3).

Eyepieces: Eyepieces are stored in the eyepiece box on the shelf in the corner of theDoghouse. Most objects are best viewed under low or moderate power, rather than highpower which is recommended only for high surface-brightness objects such as planets anddouble stars. Replace the eyepieces in the eyepiece box before leaving.

3. Finding Objects

A list of interesting objects is available on the table in the Doghouse. Coordinates maybe found in Norton’s Star Atlas. When searching for objects, always use the lowest powereyepiece (i.e. longest focal length) first. There are three basic ways to find objects:

1. By eye: Using Norton’s, or any other source, point the telescope at the appropriateregion of the sky and search for the object with the finder. This will probably not workfor fainter objects, but is suitable for the most interesting objects.

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Figure 2. 6-inch Alvin Clark Refractor. (2) Setting Circles, (3) Setting CircleMagnifiers, (5) Drive Governor, (6) Drive Push-Pull Switch, (7) Drive WindingShaft, (8) Slow Motions and Clamps, (9) Eyepiece.

2. By DEC: Carefully set and clamp the telescope at the DEC of the object as accuratelyas possible. Find the approximate location in the sky, and leaving the HA unclamped,search in the finder while moving the telescope slowly in HA. The finder is small, sofainter objects will be rather dim. Check out likely candidates in the main telescope.Small adjustments in DEC may be necessary.

3. By DEC and RA: Set the telescope to the DEC of the object and clamp. Thencalculate the hour angle from the general relation HA = ST − RA where HA is thehour angle, ST is the sidereal time, and RA is the right ascension of the desired object.If the HA is negative, the object is east of the meridian. Add 24 hours to the HA andset the telescope to the resulting HA. If the HA is positive then set the telescope to theHA directly. (NOTE: This is the procedure for the 6-inch refractor. The 10-inch HAdial goes in the opposite sense; a negative HA is west of the meridian instead of east.The strategy is the same however so just keep in mind how the dials are divided.)

Determine the ST from the sidereal clock. (Alternatively set your watch to the ST usingthe table provided in Norton’s, or from the sidereal clock in the 26-inch dome. Overa few hours, your watch will keep sufficiently accurate sidereal time for this method.)

Once the coordinates are set and the drive turned on, you may search for the object at yourleisure. You will probably have to search around a bit in the finder. Practice the methodon bright stars first. It sometimes helps to repeat the procedure, or at least double-checkthe setting circles if you can’t find what you’re looking for. If objects seem consistently andsubstantially offset in HA, the sidereal time may be wrong.

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While observing, you may need to make small corrections with the slow motions for errorsin the clock drive. It is best not to touch the telescope otherwise during observations.

At any given time, you will not be able to reach all of the listed objects. Usually, you canobserve any object whose HA is less than 3 hours. The farther north the object, the greaterthe hour angle to which you can observe it.

Note that the cardinal directions in the finder and main telescope will be inverted relativeto their orientation in the sky.

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4. Closing Down

4.1. Stow the 6-inch Clark refractor

• Park the Clark with the tube level and on the west side of the pier, with the objectivepointing south. Clamp telescope in RA and Dec.

• TURN OFF DRIVE. Wind drive, stopping when the top of the weight reaches thebottom of the access hatch. Never overwind the drive.

• Cover main and finderscope objectives. Replace eyepiece tube cover.

• Stow all eyepieces (close the box).

• Make sure you have logged your use of the telescope in 6-inch logbook.

4.2. Secure the doghouse

• Clean up table and shelves. Take all trash with you. Return all borrowed material.Stow CCD/computer, etc., in observer’s room in main building.

• Unlock roof crank and roll roof shut, making sure it clears telescopes. Lock roof cranktightly, with roof rolled firmly to its limit.

• Turn off (inside and outside) lights. Shut door, making sure it is locked.

4.3. Observer’s Room (Room 106)

• Record use of telescope (along with your name, and the number of visitors) in log bookkept in observer’s room. This is not a trouble log.

• Make sure table in observer’s room is clean when you leave.

• If you have logged in, be sure to log out of the workstation (leander). Power off themonitor.

• Report ANY problems with telescope by email to:obstrouble@mail.astro.virginia.eduAdditionally, immediate, serious problems must also be reported to the TA or RickyPatterson (214-0414 lives in Vyssotsky Cottage, can help at night, but be sure to leavea message if there is no answer) or Ed Murphy (293-5634, can help at night).

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4.4. Secure the Observatory and Grounds:

• When leaving, turn on switches for security lights in closets (Room 102 and 104A).

• Leave door to Room 102 (closet) slightly open to control humidity.

• Turn off manually controlled light switches (museum display cases, light boxes, domeand foyer).

• Make sure that inner main door LOCKS behind you when leaving, and close outermain doors.

• Close the gate. Please Note: The gate should be closed at night at ALL timesEXCEPT during a Public Night, Group Night or Telescope Observing Night. bf Itshould be closed while you are observing at the telescope, and only opened long enoughfor you to drive through.

• Contact someone IMMEDIATELY if you are unable to stow the telescope SAFELY.

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Chapter 5

The Doghouse Observatory 10-inchMeade LX200 Schmidt-Cassegrain

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10-inch Meade LX200 Schmidt-Cassegrain(Rev. August 09, 2011)

1. Introduction

The 10-inch telescope is a Meade LX200 Schmidt-Cassegrain and is found in the Doghousenext to the 6-inch refractor (see Chapter 3). The Schmidt-Cassegrain is equatorially mountedand is driven by an electric clock drive, and its motion can be operated from a hand-heldcontrol paddle. The Doghouse telescopes should not be used until you have been shown howto use these telescopes and have been given permission by a TA or faculty member to usethem on your own (i.e., checked out).

2. Operation of the 10-Inch Meade Telescope

1. Roof: The roll-off roof of the Doghouse is operated manually with the crank beside thedoor. There is a vice clamp holding the chain in place which must be loosened beforeopening the roof. Be sure to reclamp the chain tightly after closing up for the night.Never move the roof unless both telescopes are horizontal and clear of itspath. Refer to the Open/Close Checklist for the Doghouse Observatory (Chapter 3).

2. Objective Cover: Remove objective cover carefully. Be careful of the corrector platejust beneath as there is no handle on the cover. Be sure to replace it when you arefinished observing.

3. Telescope Power: Turn on the power strip located at the base of the pier on thelower east side of the pier. Then, place the ON/OFF switch located in the upperright corner of the power panel (11) to the ON position. The telescope should now bereceiving power.

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4. Declination Clamp: Loosen the declination clamp. This clamp is a palm sized knobwith a grooved edge located in the center of an aluminum ring on the outside of oneof the fork arms. Loosen the clamp by turning the knob counterclockwise. Once theclamp has been loosened, move the telescope to 0◦ declination by aligning the 0 on thedeclination setting circle (3) with the declination pointer (4) on the fork. Tighten thedeclination clamp.

5. Paddle and Drive: The paddle controls the slow motions and the drive. Use thedirection keys on the control paddle (12) to slew the telescope in the east-west directionuntil the right ascension pointer (9) is at zero hour angle. This is accomplished byaligning the right ascension pointer (9) with the hour angle pointer (16) located justabove the center of the power panel on the drive base. Note that the telescope hasvariable slew rates: slew, find, center, and guide corresponding to the buttons onthe keypad with the numbers 7, 4, 1, and 0 respectively. An abbreviation for eachslew rate is written above the corresponding number on each button. Simply press theappropriate button to change to the desired slew rate.

6. Star Alignment: The celestial coordinates must now be set by aligning the telescopewith two reference stars. At this point the menu on the control paddle should read:

→ TELESCOPEOBJECT LIBRARY

Make sure that the arrow is pointing to the TELESCOPE option and press the keymarked ENTER. The menu should now read:

→ 1) SITE2) ALIGN

Press the NEXT key to move the arrow down to the ALIGN option and then pressENTER. The menu should now read:

→ 1) ALTAZ2) POLAR

Make sure that the arrow is pointing to the ALTAZ option and press ENTER. If themenu DOES NOT change, but the checkmark on the right of the menu moves toALTAZ, press ENTER again. The menu should now read:

1 Star or2 Star Alignment

Press the key with the number 2 on it to select Star Alignment. You will now be askedto pick two stars from a list contained in the telescope’s computer. The computer willthen ask you to center these two stars in turn in order to set the coordinates for thetelescope. The menu should now read:

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Level base, thenpress ENTER

The base has already been levelled so go ahead a press ENTER. The menu now reads:

Press ENTER, pickalign star 1

Press ENTER to get a listing of the stars available in the computer’s memory. Use theNEXT and PREV keys to move the arrow to the star of your choice. Once you havefound the star that you wish to use, press ENTER. The menu will then read:

Center Starnamethen press ENTER

Use the control paddle to slew the telescope to the star that you have chosen and centerthe star in the field of view. DO NOT LOOSEN ANY CLAMPS OR MOVETHE TELESCOPE BY HAND. This will cause the computer to lose track of whereit is in the coordinate system. Once the star is centered press ENTER. The menu willthen ask you to go through the procedure of picking and centering a star once more.Press ENTER, pick a second align star just as before, USE A DIFFERENT STARTHIS TIME, center the star, and then press ENTER. The computer should now beoriented and happy. The menu on the control paddle should have returned to the firstoption:

→ TELESCOPEOBJECT LIBRARY

7. Locate Messier Object: The telescope can now be easily moved to any Messierobject by pressing the key which has an M for Messier above a number 9 on it toobtain:

M object:

Key in the Messier number of the object that you wish to find and press ENTER. Themenu now displays some information about the object such as its magnitude, whattype of object it is, etc... Press GOTO and the telescope will automatically slew tothe object. Use the control paddle to center the object in the field of view.

8. Locate NGC Object: You can just as easily find objects whose NGC number youknow by pressing the key marked with CNGC above the number 3.

9. Eyepieces: Eyepieces are stored in the eyepiece box on the shelf in the corner of theDoghouse. Most objects are best viewed under low or moderate power, rather thanhigh power which is recommended for high surface-brightness objects such as planetsand double stars. Replace the eyepieces in the eyepiece box before leaving.

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3. Closing Down

3.1. Stow the 10-inch Meade

• Park the Meade on the meridian, with the tube pointed to zenith.

• Clamp the telescope, turn off power. Hang control paddle from silver handle onsouth side of the end of the tube. Don’t hang control paddle elsewhere.

• Stow all eyepieces (close the box). Replace eyepiece tube cover.

• Make sure you have logged your use of the telescope in 10-inch logbook.

3.2. Secure the doghouse

• Clean up table and shelves. Take all trash with you. Return all borrowed material.Stow CCD/computer, etc., in observer’s room in main building.

• Unlock roof crank and roll roof shut, making sure it clears telescopes. Lock roof cranktightly, with roof rolled firmly to its limit.

• Turn off (inside and outside) lights. Shut door, making sure it is locked.

3.3. Observer’s Room (Room 106)

• Record use of telescope (along with your name, and the number of visitors) in log bookkept in observer’s room. This is not a trouble log.

• Make sure table in observer’s room is clean when you leave.

• If you have logged in, be sure to log out of the workstation (leander). Power off themonitor.

• Report ANY problems with telescope by email to:obstrouble@mail.astro.virginia.eduAdditionally, immediate, serious problems must also be reported to the TA or RickyPatterson (214-0414 lives in Vyssotsky Cottage, can help at night, but be sure to leavea message if there is no answer) or Ed Murphy (293-5634, can help at night).

3.4. Secure the Observatory and Grounds:

• When leaving, turn on switches for security lights in closets (Room 102 and 104A).

• Leave door to Room 102 (closet) slightly open to control humidity.

• Turn off manually controlled light switches (museum display cases, light boxes, domeand foyer).

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• Make sure that inner main door LOCKS behind you when leaving, and close outermain doors.

• Close the gate. Please Note: The gate should be closed at night at ALL timesEXCEPT during a Public Night, Group Night or Telescope Observing Night. Itshould be closed while you are observing at the telescope, and only openedlong enough for you to drive through.

• Contact someone IMMEDIATELY if you are unable to stow the telescope SAFELY.

Those are the basics. To learn more about all of the fancy features on the telescope consultthe LX200 manual located in the Doghouse or in the TA filing cabinets.

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Figure 1. Meade LX200 Schmidt Cassegrain Telescope

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Chapter 6

The McCormick Observatory 26-inchClark Refractor

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The 26-inch Clark Refractor

Revised September 2010

The 26-inch refracting telescope was built by Alvan Clark Sons and completed in 1875. It ishoused in the dome on Mount Jefferson; the observatory was completed in 1884, and

dedicated on April 13th, 1885. The Clark refractor has a 26-inch diameter lens with a focallength of 32.5 ft (9.9 m). Its field of view is about 0.75 of a degree with photographic plates.

This telescope has been used primarily for astrometric observations and the observatoryplate file contains over 140,000 plates which were taken between 1914 and 1995 for the

purpose of determining stellar distances and motions.

For a full history of the telescope see:

http://www.astro.virginia.edu/research/observatories/26inch/

Figure 1: The 26-inch Clark Refractor in proper stow position.

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1. A Tour of the Telescope

The dome is entered via an entrance to your left as you come in the front door of theobservatory building. There is an additional entrance located on the south side of the dome,which is not normally used (and should not be used for public access since it requires peopleto pass by mechanical equipment in the dark).

Figure 2: The dome entrance as viewed from inside the dome. The green box indicates thelocation of the light switches and plug for the dome charger.

There are three dome slits which are opened and closed by ropes which hang along the domewall. There are two floor mats near the entrance which are to collect water from knownleaks in the dome slits. The leaking water must be kept off of the original observatory floor.There is no need to move these mats (e.g. the observing chair will move over them), but ifthey need to be moved, they must be replaced in their original location.

There are two observing chairs. The larger of the two runs on a track around the edge of thedome. This track must be clear for the chair to move safely. Damage or injury may resultif the track is not clear. Please note that the chair will move freely with the floor mats inplace. A smaller chair is located opposite the larger chair. This chair can move freely andthe wheels can be locked when in use. Never lock the wheels when stowing the chair at theend of the night. There is a small box which can also be used for observing; care should beexercised, since the box can damage the floor.

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There are two sets of telescope controls. One is located on the pier and the other on a handpaddle attached to the telescope itself. The sidereal time can be read from a digital clockon the far wall and the local time is read from the analog clock on the pier.

Equipment for maintaining and repairing the telescope is stored in the dome at the Southend of the pier. This equipment should not be touched or moved.

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Figure 3: An observer adjusts the location of the telescope from the pier controls. Alsohighlighted are the locations of local and sidereal clocks in the dome.

2. Opening Procedure

1. Allow at least one hour of preparation time before your planned observations.

2. Turn on the wall switch lights which are to the left of the dome entrance (see greenbox in Figure 2). Directly adjacent to the switch is a small toggle that will adjust theintensity of the lights.

3. Unplug the dome motor battery charger (hanging cord) from the wall outlet above thelight switch, remove the extension cord and place it on the shelf in the alcove to theright of the plug. Never leave this extension cord attached when the dome motor isunplugged.

4. Open the dome shutters by pulling on the appropriate ropes.

The dome itself can be moved from both the console and the paddle using the DomeLeft or Dome Right toggle (See Figure 4 (2) or Figure 5 (4)). The dome can also bemoved from the hanging plug by holding down the left or right buttons. Always allowthe dome to come to a complete stop before changing the direction of dome motion.

Always inspect the wall of the dome to be sure that no objects will be caught by the domeropes as the dome rotates. Always use caution when rotating the dome, and watch forany potential problems. Never store objects by leaning them against the wall of thedome.

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Figure 4: Pier Control Panel

5. Turn on the telescope power from the console (top left button, see Figure 4 (1)). Thiswill activate all console controls, paddle controls and console lights. To do this pushthe Power On button on the console (note there are also power controls on the topof the hand paddle). The red indicator light on the bottom left will illuminate whenthe power is on (Figure 4 (3)).

6. To unclamp the Right Ascension (RA) or Declination (Dec) motions, press the RAClamp and/or Dec Clamp button on the control console (see Figure 4 (4)). This willrelease the telescope clamps. Red indicator lights will illuminate when the telescope isunclamped (see Figure 4 (4)).

To slew the telescope down into position for observing, unclamp the RA Clamp, pressthe West (W) slew button (see Figure 4 (8)). This will move the objective toward thewest and the tailpiece down toward the pier. Releasing the button will stop the motion.

Care must be exercised whenever the telescope is being slewed. Make sure that thetelescope’s path is clear, and always watch it as it moves. Particular care should betaken with any movements of the tailpiece near the pier.

Release the W button to stop slewing once the tailpiece is within easy reach. Again,use caution to avoid hitting the pier, or anything else.

Motion in declination works in a similar fashion (although the Dec slew motor doesnot work consistently). Unclamp the Dec Clamp to allow movement in Declination.

7. To open the lens cover, flip the objective cover toggle down (see Figure 4 (6)). Thegreen indicator light will turn red when the objective is opened.

Note: Always open the objective cover before closing the dome shutters. Sometimespaint chips or other materials on the dome slits can fall onto the objective while the

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dome is in motion or while closing the dome shutters. This can cause serious damageto the objective.

8. To rewind the RA drive sector, press the Sector Reset button on the console or handpaddle (see Figure 4 (7) or Figure 5 (2)). The indicator light will turn red as this driveis reset. When the light turns off then the drive is reset and the observer has about1.5 hours of motion available before needing to reset.

9. To turn on the clock drive, press toggle the Track switch on either the console or handpaddle (See Figure 4 (5) or Figure 5 (5)). The indicator light will turn red when thetracking is on.

Figure 5: Hand Paddle Control Panel

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3. Locating an Object

1. Pick the object that you want to observe.

Note: Any declination greater than 24 degrees will cause the telescope to hit thepier soon after the object passes the meridian. Although it may not appear obviousfrom ground level, the declination periscope (brass tube) will hit the shelf on the top ofthe pier starting at +24 degrees even though the tailpiece will clear the pier.

Amount of Time after Transit before Telescope Hits Pier

Declination Time (minutes)+23:40 Will Pass+24:00 19+25:00 18+26:00 10+27:00 8+30:00 6+34:00 6+35:00 6+40:00 5+45:00 6+50:00 9+55:00 9+60:00 10+65:00 12+70:00 21+75:00 34

2. Set the declination.

The current declination of the telescope can be read off of the declination periscope onthe side of the telescope opposite the finding scope. Gently move or slew the telescopeto the correct declination.

Clamp the telescope in declination while holding the telescope in place with the silvermetal bar around the tailpiece. Never push against the tailpiece itself. Afterclamping small adjustments can be made with the slew buttons. While clamping thetelescope will move slightly.

3. Set the Hour Angle (HA).

Compute the HA: HA = Sidereal Time RA

(A positive value indicates minutes to the west, negative indicates minutes east, i.e., ifthe RA is greater than the sidereal time the object is east of the meridian.) Read thehour angle from the large circle on the polar axis (1 division = 5 minutes).

Clamp the telescope in Right Ascension.

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4. Position the dome with an open slit over the objective lens.

Declination Coverage of the Dome Slits when Placed Along the Meridian

Shutter To South To NorthTop +6 to +45 +35 to +73

Middle -24 to +14 +67 to poleBottom -18 to Horizon

5. Use the track toggle to initiate the clock drive. The tracking only functions when thetelescope is clamped in RA.

6. Center the object of in interest in the finder scope.

Compare the star field through the finder with your finding charts. Center your objecton the cross hairs using the fine adjust slew motions on the paddle.

7. Clamp the telescope in RA. Tracking will commence as soon as the telescope is clampedin RA. Periodically check the finder to ensure that the object has not drifted out ofview.

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4. Telescope Tailpiece

The telescope tailpiece has been designed to allow for simultaneous use of the eyepiece,Astrovid 2000 camera, and an SBIG CCD. Flip mirrors located at the back end of thetelescope allow one to change between instruments. The tailpiece uses the 2 inch eyepiecesfound in the metal cabinet in the Observer’s Room.

We currently have three eyepieces for use on the 26-inch. Great care should be exercised inhandling all of the eyepieces and filters.

Available Eyepieces:

1. 20 mm Nagler Type 2 (great for use with planets!)

2. 35 mm Panoptic

3. a 55 mm Plossl

Figure 6:

Left: Eyepieces for the 26-inch are located in the metal instrument cabinet in theObserver’s Room.

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Right: The backend of the telescope with major features boxed in red. The metal bararound the tailpiece is used to move the telescope. The declination periscope is located on

the opposite side of the telescope from the finder scope.

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5. Visual Observations

Visual observations are conducted using a set of 2-inch eyepieces kept in the Observer’sRoom (See Figure 6).

1. Loosen the screws on the eyepiece holder on the back end of the telescope and removethe stop, storing it on the desktop. Slide in the desired eyepiece and tighten the screwsto lock in the eyepiece. Stow both the eyepiece cap and the stop on the desktop forthe remainder of the night.

2. The rough focus for the backend can be turned with the crank on the pier table. Arough guide to where the focus has been historically is located 45 degrees counterclockwise from the location of the rough focus. Return the focus crank to the piertable.

3. Fine focus knobs are located on the eyepiece holder on the backend of the telescope(see Figure 6).

4. Make observations!

5. When finished, remove the eyepiece and return it to the case. Replace the stop. Then,follow the close down procedures in Section VIII.

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6. Basic CCD Observations

1. Carefully roll the PC cart from the observer’s room into the dome.

2. The powerstrip on the PC cart can be plugged into the outlet on East side of the pier.

3. Connect the male end of the ribbon cable into the parallel port on the PC. Connectthe female end of the ribbon cable to the parallel port on the CCD Head.

4. Connect the 5-pin power cable from the CCD power supply to the CCD head. Plugthe power supply into the power bar on the telescope.

If everything is connected properly then, the unit now has power. The red LED on thehead of the CCD head will glow and the fan will being spinning.

5. Plug the PC and the PC monitor into the power strip on the PC cart. Start the PCby pressing the power button.

6. Insert/Check the filter. The filter is mounted in a holder just before the instrument.A set of BVR filters are stored in the Observers Room.

7. The rough focus for the back end can be turned with the crank on the pier table.A rough guide to where the focus has been historically is located 45 degrees counterclockwise from the location of the rough focus. Return the focus crank to the piertable. Fine focus knobs are located on the backend of the telescope.

8. Center the object of interest in the eyepiece as described in Section III.

9. Fine focus for the CCD camera is located on a knob near where the CCD attaches tothe tailpiece.

10. Flip the mirror to send the light into the instrument.

11. Image the Object. A PC is required to control the CCD. The CCD is controlled bythe Maxim DL software, which operates in the Windows environment.

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7. Warnings and Additional Instructions

1. Do not leave the telescope unattended with the drive running. If leaving the dome forany length of time close down the telescope.

2. The sector is located behind the Right Ascension drive. For historical reasons (theoriginal drive was a weight driven governor clock drive, with a weight that had to bereset every 90 minutes), the main gear for the RA drive is only a small section of a fullcircle. This will drive the telescope for about 1.5 hours, after which the sector mustbe reset. You are advised to reset the sector

3. Remember that the 26-inch can not point to all places in the sky. The telescope isalways on the West side of the pier, never on the East. This means that you should tryto observe objects before they transit, especially northern ones. You will have to bemindful in your observing plans in order to ensure you can observe the desired objectswithin these limitations.

4. The Observer’s Room contains the Astronomical Almanac, Norton’s Star Atlas and theSAO Catalog. The computer in the Observer’s Room is connected to the department’snetwork. The 26-inch observing logbook is also located here. Please do not forget tofill out the log when you observe.

5. There is a phone on the east side of the pier and a phone in the Observer’s Room.There is a list of departmental phone numbers on the wall in the Observer’s Room aswell as a list of the emergency contacts.

6. There is a First-Aid kit in the Observer’s Room in the built in bookshelf.

7. There are pressurized water fire extinguishers in the entry hall and the lecture room.These should not be used on electrical or chemical fires. A small extinguisher for alltypes of fires is located downstairs in the room outside of the bathroom.

Call 911 (9-911 from a University phone) before attempting to put out thefire by yourself.

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8. Closing Down

1. Turn off the RA Drive and reset the sector. The reset is complete with the red indicatorlight turns off (see Figure 4 (7) or Figure 5 (2)).

2. Close the objective cover using the console (see Figure 4 (6)). The indicator light willturn green when the cover is completely closed.

Note: Always close the objective cover before closing the dome shutters. Sometimespaint chips or other materials on the dome slits can fall onto the objective while thedome is in motion or while closing the dome shutters. This can cause serious damageto the objective.

3. The telescope stow position is: +38 degrees declination and HA of 4 hours east. Bringthe telescope down so that the objective cover points at the zenith. The telescope tubeshould be parallel to the pier. Then, use the RA slew to move the telescope 4 hourseast.

If you are unable to safely stow the telescope, call for help immediately.

4. Clamp the telescope in RA and Dec. The red indicator lights will turn off when thetelescope is clamped (see Figure 4 (4)). If using the CCD, shut down the CCD beforeturning of telescope power.

5. In general, green indicator lights mean that it is okay to leave the telescope and thedome (except for the on red light which simply indicates that the power is on). Redindicator lights mean that some aspect of the telescope is not in the proper mode fortelescope storage. If the objective cover light is green and no other indicator lights areilluminated aside from the red power light, then turn off power to the telescope withthe button on the pier. The red indicator light will turn off when the power is turnedoff (see Figure 4 (1)).

6. Close the dome shutters completely. Close the shutters by using the ropes. Often theshutters will stick when very close to being closed. Be sure to give a strong hard tugto make sure the shutters are completely closed. You must visually inspect the domeshutters to ensure they are completely closed. The dome shutters will make a soundeven when they are not completely closed, thus only hearing the shutters close is notenough to confirm they are closed.

7. Rotate the dome so that the charger cord is hanging just to the right of the outlet.Plug in the extension cord, and plug in the dome charger (See Figure 2).

8. Clean up the area before leaving. Be sure to return all objects to their proper storagelocations.

(1) Carefully push the large observing chair past the second window on the left side ofthe room. Return the small observing chair to the west side of the room against thetrack and next to the historic tailpiece jack. Do not lock the wheels when stowing the

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small chair. Make sure the box is against the pier, being careful to not damage thefloor.

(2) Return ladders or any other equipment to its location against the pier.

(3) Ensure that the focus crank is on the desktop on the north side of the pier.

(4) Return all reference materials to their proper locations in the Observer’s Room.

(5) Return the computer and other equipment to their proper locations in theObserver’s Room.

(6) Return the eyepieces to the closet (stowed in their case).

9. Turn off lights in the dome and close the door to the dome.

10. Observer’s Room:

(1) Record use of the telescope in the log. Please record ONLY your name, purpose oftelescope use (e.g. Astr3130) and the number of visitors.

(2) Log out of the computer in the observer’s room and return books and otherequipment to its proper place. Turn off the monitor.

(3) Report any and all problems to: obstrouble@mail.astro.virginia.edu

Immediate, serious problems must also be reported to the TA or RickyPatterson (214-0414; lives in Vyssotsky Cottage beside the observatory; availableat night) or Ed Murphy (293-5634; available at night).

The TA is your first access point for help. If you are unable to reach either TA,then contact your professor or another faculty member at the department. Phones arelocated both in the dome and in the Observer’s Room. In the Observer’s Room is alist of phone numbers for members of the Astronomy department. It is critical thatproblems be reported in a timely manner.

11. Secure the observatory and grounds.

(1) Lights in most of the observatory are on motion sensors and will turn themselvesoff after you leave. It may seem disconcerting to leave the observatory with lights on,but do not turn off the motion sensors; the next person who arrives after dark willthank you!

Lights in the dome room and entrance are not on motion sensors. Be sure to turn offthese lights when leaving.

(2) Leave the door to the Observer’s Room open and leave the door to the closet (withthe security light switches) slightly ajar to control humidity.

(3) Turn on the outdoor security lights in the closet.

(4) Make sure the inner door locks behind you as you leave.

(5) Close the outer doors. Make sure that the left-hand outer door is bolted. If youclose both doors without bolting the left-hand door, it can be very difficult to openthe doors.

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(6) Close the gate. The gate should be closed at all times (at night) except duringpublic events (e.g. public night). It should be closed while you are observing at thetelescope, and should only be opened when driving in or out. Never leave it openfor someone who is due at any minute; they will have to open and close the gate forthemselves).

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9. Opening Checklist

1. Turn on Lights.

2. Open Dome Slits. Unplug Dome Charger and stow extension cord.

3. Turn on telescope power and drive.

4. Unclamp the telescope, slew it so the tailpiece is accessible, reset the sector.

5. Open the objective cover.

6. Turn off main lights, prepare to observe.

10. Closing Checklist

1. Turn off the RA drive. Reset the sector.

2. Close the Objective Cover.

3. Stow the telescope at +38 degrees, and HA = 4 hrs east. Clamp the telescope in bothRA and DEC.

4. If using the CCD, turn off power to the CCD. Turn off power to telescope.

5. Close the dome shutters completely, visually inspecting the slits. Do not rely on thefeel of resistance on the dome pulley rope as an indication that the slit is completelyclosed.

6. Align the dome correctly and plug in the dome motor.

7. Clean up the area before leaving. Be sure to return all equipment to its proper storagelocation within the dome or Observer’s Room.

8. Turn off light in the dome. Close the door to the dome.

9. Sign the log book and clean up the Observer’s Room.

10. Secure the Observatory and Grounds. Be sure that the security lights are on at theobservatory, the observatory is locked and that the gate is closed.

11. Contact someone immediately if you are unable to stow the telescope safely. Reportall problems to obstrouble@mail.astro.virginia.edu

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54

Chapter 7

The Fan Mountain Observatory40-inch Astrometric Reflector

55

56

The Fan Mountain 40-inch Telescope(Rev. August 15, 2011)

1. Introduction

Figure 1. The Fan Mountain 40-inch Telescope.

This manual gives general instructions for operating the Fan Mountain 40-inch telescope,the filter control system, and the autoguider.

Fan Mountain Observatory is a research facility of the University of Virginia Department ofAstronomy. The instruments are being used for graduate student teaching and the researchprograms of faculty and their students. You should conduct your work with the utmost care,patience, and forethought, keeping in mind that the equipment is delicate, complex, andexpensive to maintain.

To minimize the potential for accidents, you should have a clear idea of your observing planfor the night, including the optimal observing times of your target and calibration objects,lists of coordinates and finder charts, and an efficient plan for minimal changing of filters.Do not neglect to obtain the necessary set of bias frames and flat fields for calibration, orthe rest of your data will be worthless.

If anything in this manual is unclear, consult the TA or appropriate faculty member forclarification. As with all delicate equipment, NEVER force any moving part beyond reasonable

57

and expected resistance. Always keep track of the telescope position in relation to the sky,dome, and objects within the dome. NEVER touch any optical element. Oils from your skinwill permanently embed into glass surfaces and optical coatings. It is better to leave smallamounts of dust on optical surfaces than to risk scratching or marring them with attemptsat cleaning. If dust is a serious problem, ask the TA, Jim Barr, Charles Lam, or a facultymember to remove it with dry nitrogen. If, while in the control room, you hear any peculiarnoises or have any uncertainty about the location of the telescope or dome, you should makethe trek up one flight of stairs to check the dome in person. If you are uncertain aboutany aspect of operating the telescope, or any other piece of instrumentation, STOP and asksomeone. THINK BEFORE DOING.

Home phone numbers: Fan Mountain caretaker Nick Nichols (979-0684), David McDavid(434-985-4378), Jim Barr (540-832-5304), Steve Majewski (434-975-6435). In case ofemergency don’t hesitate to call, but please try not to call unless it is absolutely necessary.

2. Description

The Fan Mountain 40-inch telescope has an f/13.5 Schmidt-Cassegrain optical system with a40-in (1-m) aperture, a focal plane image scale of 15.3′′ mm−1, and a corrected photographicfield of 50′. It has a computerized telescope control system (TCS) developed by DFMEngineering, Inc. and described in detail in the TCS486 Operations Manual on the bookshelfin the control room.

A pair of fans inside the telescope tube near the corrector plate can be turned on with thetoggle switch on the west side of the telescope tailpiece. Power to the toggle switch is ononly when the CCD switch on the bottom rack panel (Fig. 2) in the control room is on.Running these fans helps to improve tube seeing under some conditions.

3. Startup Procedure

1. Begin filling out a new log form in the blue Observing Log notebook which is kept onthe bookshelf in the control room.

2. The CCD switch on the Rack Panel (Fig. 2) controls a large uninterruptible powersupply (UPS) and is normally left ON all the time. If it is not already on, turn iton and leave it on.

3. Power up the autoguider PC if it is not already on. It will boot to a Windows 7 logonprompt. Turn on the telescope control PC (the one in the electronics rack on the farright side of the table). It will boot to a DOS prompt. This PC shares the largemonitor and keyboard in the middle of the table with the autoguider PC (which mustbe powered up first) through a pushbutton toggle switch with LEDs indicating whichsystem is selected.

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Figure 2. The Rack Panel.

4. At the telescope control PC DOS prompt, enter tcs to start up the DFM TelescopeControl System. Set the date and the universal time, referring to the clock in theelectronics rack for the local time. To do this:

• Start from the Main Menu (press ESC if it is not displayed)

• Enter 1 (Initialization Menu)

• Enter 1 (Set date and time)

• Fill in the blanks with the date and UT

• The TCS will assume the telescope is pointed at the zenith and will approximatelyinitialize the coordinates based on the latitude, longitude and local sidereal time.

5. Set the switches on the DFM panel (Fig. 3) to Track, Track Off, Drives Off, AutoDome Off, External Computer On, and Dome Home, then turn on the Motor DriveChassis, Motors On, and Drives switches.

Figure 3. The DFM Panel.

6. At the telescope control PC DOS prompt, enter tcs to start up the DFM TelescopeControl System. Set the date and universal time, referring to the clock in the electronicsrack for the local time. (Start from the Main Menu (press ESC if it is not displayed),

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enter 1 (Initialization menu), enter 1 (Set date and time), then fill in the blanks.) TheTCS will assume the telescope is pointed at the zenith and will approximately initializethe coordinates based on the latitude, longitude, and local sidereal time.

7. Upstairs in the dome, use the ladder to connect the shutter power cord from theelectrical outlet to the shutter motor box and turn the knob on the motor boxcounterclockwise. The shutter will open and automatically stop when it is done.Unplug the power cord from the motor box. If you don’t, you’ll destroy the cordor the connectors when the dome moves and you will be in serious trouble when youneed to close the dome.

8. Turn on the TCS monitor on the desk in the dome. This monitor and keyboard willfunction even when the shared monitor and keyboard in the control room are beingused by the autoguider PC. Adjust the brightness and contrast as desired. Whenworking in the control room and taking data, you will usually want to have this screendim.

9. Use the control paddle (Fig. 4) to slew the telescope to the North (towards the horizonin the direction of the desk in the dome room) just far enough so you can reach andremove the telescope lens cover by climbing up the ladder to the upper level. Strapthe lens cover to its stand on the upper level so the wind won’t blow it away.

DFM EngineeringIn Out

Focus

Slew

N

S

W ESet

L RDome

Figure 4. The Dome, Focus, and Telescope Control Paddle.

10. Horizon Limit: You may find that you have passed the TCS horizon safety limit inslewing the telescope to the North to get to the lens cover, and the telescope will nolonger move by motor control. If this happens, go back to the control room, turn offthe Drives and Motors On switches on the DFM panel, then go back to the domeand push up on the telescope tube by hand while standing on the upper platform tomove it in declination until it points well above the horizon. Then go back to thecontrol room and turn the Motors On and Drives switches back on. For the safety ofthe telescope, go back to the dome and use the paddle to verify that normal motoroperation is restored.

11. Use the paddle to slew the telescope back to the zenith.

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12. With the dome slit facing South (AZIMUTH 180.0), which is the HOME position, turnon the Dome Track and Auto Dome switches on the DFM control panel so the domewill automatically follow the telescope.

13. In the TCS Main Menu enter 4 (Miscellaneous menu), enter 1 (Set switches), then turnon RATE CORRECTION, which will enable automatic track rate correction derived fromthe mount model parameters currently compiled into TCS, and DOME, which must beconsistent with the setting of the Auto Dome switch on the DFM control panel.

14. In the TCS Main Menu enter 3 (Rates Menu), enter 1 (Set Track Rates), then input14.980 for the RA rate and leave the rest of the fields blank. Press Enter for thechanges to take effect.

15. Turn on the Track switch on the DFM control panel to start the telescope tracking.

4. Initializing the Coordinates

1. For the safety of the telescope, always do this operation in the dome.

2. Pick a star near the zenith from the BRIGHT STAR LIST in the AstronomicalAlmanac. In the TCS Main Menu enter 2 (Movement menu), enter 1 (Set slewposition), then enter the coordinates and their associated equinox. When TCS asks“Any Changes?” respond with a RETURN.

3. In TCS, enter 7 (Start slew). Be prepared to stop the telescope if it should wander offto extreme angles. You can do that by entering 8 (Stop slew).

4. Center the star in the finder scope eyepiece, assuming it is aligned with the main scope.If you aren’t sure you have the right star, check it in Norton’s Star Atlas on the deskin the dome.

5. From the TCS Main Menu, enter 1 (Initialization menu), enter 2 (Set telescopeposition), then enter once again the coordinates and equinox for the star you justcentered. This will update the telescope position in TCS to the correct coordinates.

6. To set the TCS coordinate display to any desired equinox, start from the Main Menu,enter 4 (Miscellaneous menu), enter 2 (Set display equinox), then enter a decimal year.

5. Shutdown Procedure

1. Set the DFM panel switch to Dome Home to send the dome to the home position(AZIMUTH 180.0). Wait for the dome to go home, then switch Auto Dome Off.

2. Using the paddle, point the telescope low to the North over the upper dome platformand replace the lens cover.

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3. Plug in the shutter power cord, and turn the knob clockwise to close the shutter.Unplug the power cord from the motor box after the shutter has closed.

4. Turn off the DFM Panel Track switch, then slew the telescope to the zenith with thepaddle.

5. Turn off the Drives, Motors, and Motor Drive Chassis switches on the DFM Panel.

6. Do NOT turn off the CCD switch on the Rack Panel. Leave it on.

7. Turn off the telescope control PC power switch.

8. Finish filling out the Observing Log notebook and return it to the bookshelf in thecontrol room.

6. The Filter Control System

The filter wheels inside the telescope tailpiece above the CCD camera shutter can be operatedfrom the filter control panel on the south face of the tailpiece when the switches are set toLOCAL or from a computer in the control room when the switches are set to REMOTE.When used with the GenI CCD camera the filter wheels can also be operated from the cameracontrol program through a popup window, and filter information is recorded automaticallyin the image FITS headers (see documentation for the GenI camera).

Filter wheel A (the lower one, also known as filter wheel 1) has 4 openings spaced at 90◦

intervals and holds 6-in square filters. Filter wheel B (the upper one, also known as filterwheel 2) has 6 openings spaced at 60◦ intervals and holds 4-in square filters.

To load a filter into a filter wheel, first open the filter wheel access door (the rectangularpanel above the filter control panel held shut by clamps) so you can see the filter wheelsinside the tailpiece. Switch the filter wheel to LOCAL and use the SLEW button on thefilter control panel to rotate it. Open the lock at the edge of the filter opening you select,slide the filter into the slot, then close and gently screw down the lock with your fingers.The filter opening in the telescope light path is the one diametrically opposite the one atthe access door.

1. To control the filter wheels remotely, begin by turning on the filter PC (white tower)underneath the table in the control room. It shares the monitor and keyboard in themiddle of the table with the autoguider PC through a splitter switch. The filter PCboots to a DOS prompt.

2. Enter cd c700\motion at the DOS prompt to get to the correct directory. If thedefault filters.txt file does not correspond to your arrangement of filters in thefilter wheels, make a new file in the same format which does. Then enter motion tostart the filter control program. Ignore error messages about No blank found.

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3. When the program asks Hit Return when wheels are homed?, go upstairs to thedome and HOME both filter wheels under LOCAL control if you have not alreadydone so. Then switch both wheels back to REMOTE and go back down to the controlroom.

4. Now enter a RETURN in response to the Hit Return when wheels are homed? prompton the filter PC. Enter ? to get a list of commands. The command goto filternameshould place the filter you specify in front of the detector. Experiment with issuingcommands and going upstairs to verify the actual filter wheel positions until you aresure the system is set up correctly.

5. After this point, if you move the filter wheel under LOCAL control and wish to goback to REMOTE, exit and restart the motion program on the filter PC as describedearlier. Otherwise the program may not indicate correctly which filter is in the beamat any time.

Available filters include standard 4-in square UBVRI and 6-in square Washington filtersets, a 4-in square H-alpha/red continuum interference filter pair, 4-in square H-beta, OIII,NII, and SII interference filters, and a small collection of other assorted interference filters,including a DDO51 filter. The filters are stored away from moisture, dust, and extremesof temperature in wooden boxes on the table below the bookshelf in the control room andshould be kept there except for periods of active use when conditions are not potentiallyharmful.

Filter observations can be calibrated with observations of Landolt standard stars listed inthe catalog on the bookshelf in the control room. See other references on the bookshelf fordetails of the filter characteristics, instructions on using IRAF to reduce CCD photometrydata, and methods for the transformation of CCD photometry data to standard systems.Some useful references are:

• Landolt, A. U. 1992, AJ, 104, 340 (standard star catalog including finder charts)

• IRAF Photometry Documentation (see http://iraf.noao.edu/docs/photom.html)

• Sung, H., & Bessell, M. S. 2000, PASA, 17, 244

7. The Telescope AutoGuider

Almost all research facility telescopes are equipped with an auxiliary autoguider, a devicethat assists the main telescope in tracking a target for a longer time than the telescope aloneis capable of. The 40-inch Fan Mountain telescope can track a star unaided for approximately3 minutes (when pointed within ≈ 20◦ of the zenith). With the autoguider, exposures of upto 30 min have been tested, and longer ones are possible. The autoguider was built duringthe summer of 2001 by Jim Barr, Jeff Crane, Charles Lam, Eugene Lauria, and KiriakiXilouris.

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Figure 5. The Autoguider mounted on the 40-inch.

The autoguider consists of a CCD video camera (SBIG STV) connected to an 8-inch MeadeLX Schmidt-Cassegrain telescope that is mounted on the main telescope tube, supportedby a pivot stage. This structure enables limited but independent motion of the Meade withrespect to the main telescope tube, increasing the possibility of finding a guide star close tothe target area. Between the Meade and the STV there is a focal reducer to optimize theimage scale for autoguiding and a JMI motorized focusing stage to enable remote focusingof the guider from the control room. The manual focus knob on the Meade telescope hasbeen disabled and should not be used. Characteristics of the autoguider system are given inTable 1.

The autoguider can be controlled from its controller box, which is mounted on the west sideof the telescope tailpiece, or remotely from the control room using the autoguider PC andthe SBIG STVRemote application software. The pivot and the focusing stages are normallyoperated from the control room. A special cable is available to operate them from the domeroom.

Aperture 200 mmResolution Limit 0.69 arcsecFocal Length 2000 mm (EFL 1190 mm w/focal reducer)Focal Ratio f/10 (f/5.95 w/focal reducer)Image scale 103 arcsec/mm (173 arcsec/mm w/focal reducer)STV pixel size 7.4 microns (640x480 pix)STV pixel scale 0.76 arcsec/pix (1.28 arcsec/pix w/focal reducer)STV Field of View ∼6x8 arcmin (∼10x13 arcmin w/focal reducer)

Table 1. Characteristics of the autoguider system.

To operate the Autoguider make sure that:

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1. There is power to the tailpiece of the telescope.

2. The STV controller box in the dome is turned on.

3. The parallel cable from the camera head is connected to the controller box.

4. The video cable is connected to the controller RCS port marked Video Out via anRCA to BNC adapter and is routed through the dome floor to the control room.

5. The Serial I/O (RS232) cable is connected to the controller and is routed through thedome floor to the control room.

6. The video monitor cube on the computer table in the control room is turned on andis connected to the video cable from the controller box in the dome.

7. The Serial I/O cable from the dome is connected to a serial port of the autoguider PCin the control room.

8. The autoguider PC in the control room has Window 98 up and running. It shares thelarge monitor and keyboard in the middle of the table with the TCS PC through asplitter switch.

Figure 6. The STV virtual control panel window on the autoguider PC.

On the autoguider PC click on the STVRemote icon to start the remote control software (SeeFig. 6.) You will normally see “Link Established” in the PC Message window as the seriallink to the controller box is automatically established. If you do not, you may need to selecteither COM1 or COM2 (whichever works) from the Link pulldown menu to establish thelink.

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7.1. Setup Procedure

Click Setup, then click Parameter to cycle through the Setup menu. Click Value to adjust a

parameter. Most of the Setup parameters should be correct by default, but you can easily

cycle through the choices and select any options you want. You can dismiss the Setup menu

by clicking Setup again. All the buttons on the STV Remote virtual control panel work

according to this model.

7.2. Internal Filter Wheel

A filter wheel inside the STV camera head allows selection of an R, G, B, or Clear filter

to approximate the passband being used by the imager on the main telescope in order

to reduce autoguiding error due to differential atmospheric refraction. The filter position is

changed from the Setup procedure described above, where it appears as one of the adjustable

parameters.

Sometimes a commanded change of filter or the function of “Covering the CCD” in Tracking

or Calibration mode will stall, but this is easily remedied. Click Setup and advance to “Adj

Filter” in the Setup menu sequence by clicking Parameter a few times. If the display reads

“Fail”, click Value repeatedly to adjust the displayed voltage until the “Shtr” position is as

close as possible to the optimum value of 7.5%. The display will then begin to read “Pass”

and the malfunction will be corrected.

7.3. Image Procedure

To begin taking images click Image, then click Parameter repeatedly to see the adjustable

parameters, then set each one by clicking Value. Choose a likely exposure time (say 5–10 s),

set Continuous, then click Image again to start a continuous video stream on the monitor

cube.

7.4. Focus and Finding Procedure

Focus the 8-inch Meade by pushing the buttons on the focus hand paddle on the control

room table while watching the video monitor. You can adjust the focusing speed with the

rotary button between the IN and OUT focus buttons. Move the Meade about its zero

point position with the small hand paddle on the table to find a star if none appears on the

monitor.

When you have the 40-inch pointed at an object and are ready to set up for autoguiding,

use the same procedures to find a bright guide star and an appropriate exposure time and

to adjust the focus for the filter you have selected.

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7.5. Calibrate Procedure

Click Calibrate and set AUTO Mode. Click Calibrate again to start the STV automaticallylearning how far and in what directions its four relays move the telescope for guiding, byexercising the relays and measuring the resulting displacements of the selected guide star.If the calibration sequence is successful, the Message window will show “Passed” and themonitor cube will display four arrows showing the motions produced by the relays.

7.6. Track Procedure

To start tracking click Track, set AUTO Mode, and click Track again. The tracking statuswill be displayed on the monitor cube and in the Message window.

7.7. Monitor Procedure

The Monitor functions include monitoring the seeing, checking the optical quality of theMeade, and measuring the periodic errors in the drives.

7.8. Many More Features

If the STV doesn’t behave the way you expect it to, consult the Operating Manual STV formuch more detailed information on its operation. You will also find many more functionswhich are not mentioned here, as well as complete instructions for running the AUTO Modeprocedures manually with a great variety of interactive options.

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68

Chapter 8

The Fan Mountain Observatory31-inch Tinsley Reflector

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31-inch Tinsley Reflector(Rev. August 06, 2007)

1. General Information

The 31-inch (79 cm.) Tinsley reflector is located on Fan Mountain. The telescope isa general use reflector originally used with photomultipliers and a photographic platespecrograph. Currenty extensive hardware upgrades and instrumentation efforts areunderway to transform the observatory into a more modern research facility capable ofIR imaging and grism spectroscopy. This upgrade and instrument project is funded throughan NSF grant. Projects in the upgrade include: a drive system upgrade, a new IR Carmera,and an autoguider.

Due to the status of this upgrade project the 31-inch will only be avaialable for public nights,twice a year. For more information about the project or use of the telescope please contactMichael Skrutskie (mfs4n@virginia.edu)

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The 31-inch (79 cm.) Tinsley reflector is located on Fan Mountain. Here is some informationabout the telescope.

CommentsPrimary 31 inches in diameter, 120-inch focal length, 6.25 inches thick,

wt. = 368.8 lbs., the hole is 8.75 inches in diameter. Allmirrors are Pyrex.

4X Secondary 8.48 inches in diameter, 1.75 inches thick. System focal length480 inches. f/16

8X Secondary 5.474 inches in diameter, 0.875 inches thick. System focallength 960 inches. f/32

Plate scale 16.9 arcsec/mm (calculated). Measured value = 16.2 (Zissel)to 17.5 (Rosenberg) arcsec/mm.

Limiting visual magnitude Estimated at approximately 16 mag. on the best nights.

Dome 24 ft. Observa-dome.

Field PowerFinderscope 5” Maksutov 30’ 75X

3” finder 2-3 15XEyepiece Black 15’

25 mm. + Xfer system 2.75’ 960X25 mm. 6’ 480X

12.7 mm. 2’ 950X

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2. Care of the Telescope

The telescope should always be stored in a horizontal position in order to prevent theaccumulation of moisture on the main mirror. The telescope should not be left unattendedfor more than a few minutes unless you turn off the drive and either move the slit away fromthe telescope or close the dome shutters.

3. Opening Up

1. Locate light switches. The red and white lights in the dome room are controlled byrotary dimmer switches to the right of the door as you walk in.

2. Open dome shutter.

The dome shutter is opened and closed by plugging in the plug hanging from the rightside of the shutter. Plug into the wall outlet and hold switch in direction wanted (opento right, close to left). Letting go of switch will stop the dome shutters. Be careful notto break chain when dome is fully open or closed. The limit switches do not alwayswork.

Unplug and hang the cord over the extension arm after the slit is open to prevent thecord from catching on projections as the dome is rotated.

3. Turn on telescope main power switch on the west side of the pier.

4. Open primary mirror covers, remove covers for secondary mirror and finder scopes.

The main mirror cover can be removed by simply pulling on the handles on the swingopen doors. The doors are held closed by two latches (one at the top and the otherat the bottom of the doors when the telescope is horizontal) which will give underpressure. Rotate the small catches into the handles to ensure the doors stay open. Thedoors must be pushed closed individually, closing the one closest to pier first.

The secondary cover is removed by grabbing the handle and rotating the cover untilthe slots line up with the catches; the cover can then be pulled off. Be careful whenremoving and replacing the cover and make sure that the slots and the catches arealigned.

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5. Push set button on control console next to drive rate switches.

6. The RA and DEC. clamps, dome rotation, focus, slow motions, and offset triggerare located on the control box hanging from the telescope. Auxiliary dome rotationcontrols are located on the panel above the console.

7. The drive is turned on by the switch on the upper left corner of the console.

8. Go to the Control Room

4. The Control Room

The telescope is controlled electronically by a computer system which is composed of entirelycommercial hardware and software. The hardware and software manuals can be found inthe Control Room.

Initializing the coordinate readout software:

1. Starting the alignment procedure.

(a) Move the cursor to the Telescope option in the menu bar at the top of the screenusing the mouse.

(b) Press and release the left mouse button. The Telescope menu will appear.

(c) Move the cursor to the Link option in the menu.

(d) Press and release the left mouse button. The Link menu will appear.

(e) Move the cursor to the Establish... option in the menu.

(f) Press and release the left mouse button. The ‘Alignment Procedure windowwill appear on the screen directing you to start step 2.

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2. North Celestial Pole alignment.

(a) Point the telescope at 90 degrees declination (the north celestial pole).

(b) Move the cursor to the OK button in the Alignment Procedure window usingthe mouse.

(c) Press and release the left mouse button. The Alignment Procedure windowwill change directing you to start step 3.

3. First alignment star.

(a) Changing the alignment star (optional)

Use the menu bar and icons below it to display the desired star on the screen.

Use the mouse to place the cursor on the desired star.

Press and release the left mouse button. The Object Identification windowwill appear displaying information about the star and buttons.

Move the cursor to the Alignment Star button in the window using themouse.

Press and release the left mouse button. The display will now show the desiredstar as the alignment star.

(b) b) Point the telescope at the alignment star.

(c) c) Move the cursor to the OK button in the Alignment Procedure windowusing the mouse.

(d) d) Press and release the left mouse button. The Alignment Procedure windowwill change, directing you to start step 4.

4. Second alignment star.

(a) Changing the alignment star (optional) - See section 3a.

(b) Point the telescope at the alignment star.

(c) Move the cursor to the OK button in the Alignment Procedure window usingthe mouse.

(d) Press and release the left mouse button. The angular separation that the encodersswept out, the calculated angular separation between the two alignment stars andtheir difference will be displayed in the Alignment Procedure window. Thedifference is zero if the alignment is perfect.

(e) If the alignment difference is less than five degrees move the cursor to the Acceptbutton in the Alignment Procedure window using the mouse.

(f) If the alignment difference is greater than five degrees move the cursor to theReject button in the Alignment Procedure window using the mouse. Restartthe alignment proceedure at step 1. If the difference persists, a hardware problemis the most likely cause.

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(g) Press and release the left mouse button. The display will use the Night Visioncolors and display a bulls-eye indicating where the telescope points on the sky.As you move the telescope the bulls-eye will move accordingly. The telescope nowhas control over the screen so that the bulls-eye never leaves the screen.

5. Changing the position display.

(a) To select a numerical display of the telescope position instead of the defaultgraphical display:

Move the cursor to the Telescope option at the top of the screen using themouse.

Press and release the left mouse button. The Telescope menu will appear.

Move the cursor to the Digital Setting Circles... option at the bottom ofthe menu.

Press and release the left mouse button.

(b) To change back to the graphical display, press and release the left mouse buttonor space bar on the keyboard.

6. Temporarily regaining manual control of the display.

(a) Move the cursor to the telescope icon at the top of the screen and under the menubar.

(b) Press and release the left mouse button. The icon will change, indicating thattelescope control of the display has been disabled.

(c) To re-enable telescope control, repeat steps A and B.

5. Closing Down

1. Turn off drive.

2. Place the telescope in a horizontal position and cover both primary and secondarymirrors. Make sure both top and bottom catches on the primary doors are fastenedand that the secondary cover is completely on. Replace covers on finders.

3. Close dome by rotating the dome until the cord is near a socket. Unhook the cord andplug it in. Make sure slit is completely closed.

4. Fill out log with closing information.

5. Turn off all lights and check that nothing has been left on.

6. Close and lock the door behind you.

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6. The Control Paddle

RA and DEC clamps: These switches unlock the RA and DEC axes. When the lightsabove the switches are on the axis is unlocked. These switches control locking motors sothe lock takes a few moments to act. If the switch is thrown or reversed rapidly, the state ofthe lock might not change. (Sometimes throwing the switch fails to do anything.) If the axisfails to respond as expected, recycle the switches. When the declination axis is unclamped,the declination slow motion centers (the slow motion is a motor driven offset arm and it canrun out of travel). Sometimes, this motor “runs away” and runs the arm to the limit. Suchaction causes an abnormal noise and should be countered by pressing the reset button. (Thiscan happen spontaneously as well as when the axis is unclamped, and it always happenswhen the power is turned on.)

Focus: This switch racks the secondary in and out in order to focus the telescope. This isconnected with the focus readout on the desk.

Dome rotation: Rotates the dome. Up is clockwise, down is counter-clockwise.

Fast-Slow switch: Sets the slow motion rate to fast or slow at the operators discretion.Up is fast, down is slow.

Slow motions: The four buttons actuate the slow motions. The center switch changes thedirections of the buttons (the northward dec changes to southward, the westward RA buttonis now eastward, etc.). If the slow motions balk or act with abnormal noise, 1) check rateand make sure right speed is selected; 2) recycle locks; 3) hit reset; 4) hold button and themotion might straighten out on its own. (This is the last resort.)

Spare: Not connected to anything.

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7. The Guide Box

The guide box was designed to provide finding and guiding optics so they would not haveto be duplicated on each piece of equipment. To this end the box contains an angled mirrorto intercept the light beam. The mirror is controlled by a knob on the left side of the guidebox. This knob has three positions: full clockwise, which moves a small hole into position inthe middle of the light path; a center position, which completely intercepts the beam withthe mirror; and a full counter-clockwise position which intercepts virtually none of the lightbeam as it moves a large hole into position.

The guide box also contains two power panels for powering equipment on the tailpiece. Thesepanels are normally “cold” and have to be plugged in to power to operate. The best placeto plug in the panels is the 110V and 6.3V socket on the telescope close to the declinationaxis. The back left power panel can be plugged in there and the front right panel can beplugged into the back panel.

The whole guide box can be rotated into a comfortable position by loosening the single setscrew in the base of the telescope. Be careful not to break power cords running from theguide box to sockets elsewhere when rotating the guide box.

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8. Alcove and Circuit Breakers

The alcove of the dome contains the circuit breakers and power supply for telescope, withthe exception of the main circuit breaker which is located in the “garage” of the stationhouse. (It is marked “small bldg.” and is #16.)

The alcove switch controls the overhead light in the alcove; the outside switch controls thewhite light just outside the door. The switch marked “station house” controls the brightoutside light on the bridge from the station house to the 1 meter dome.

Figure 2 gives the layout of the outside wall. The main fuse is on the 220V. line cominginto the dome. If any unusual electrical connections seem to be occurring, particularly if thedome will not rotate, it could be due to one side of the 220V line being bad. The powerrack in the dome is the power supply for the telescope. Usually any electronics necessaryfor the instrumentation on the telescope, such as photometers etc., is located in a separaterack. Underneath the desk on the rack is the power supply proper. This contains the on-offswitch for the telescope and, on the right side, the rest button for the setting circles. Italso contains a switch to reverse the sense of the slow motions depending on which side ofthe pier the telescope is. Under the power supply is a panel of fuses marked according tofunction; under this is a panel of indicator lights to indicate the status of the various relaysthat control motor direction, etc., for the telescope.

The heaters and air conditioner in the dome were originally intended to provide a dual serviceof temperature control and dehumidification. The intent was that the air conditioner wouldkeep the dome cool during the day while the heater would prevent dew from forming. Thehumidistat should be off while observing.

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9. Equipment used with 31-inch telescope

1. Single-channel pulse counting photometer

2. Dual-channel photometer

3. The Ridell-Spotz Spectrograph

4. An Eyepiece

EQUIPMENT LOCATIONOffset guide plate FanBlack eyepiece plate Fan1 1/4 inch eyepiece focusing mount FanBlack eyepiece Fan25 mm eyepiece Fan12.7 mm eyepiece Fantransfer system Fan8X secondary Shop4X secondary on telescope

FILTERS SET CONDITIONStromgren Set 1 poor

Set 2 poorSet 3 poor u labeled non-standard

Johnson Set 1 o.k.Set 2 o.k.

DDO λ4166 very goodλ4516 very goodλ4256 very good

Hβ w&n Set 1 very badSet 2 very bad

Hα w&n terrible

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10. Log Procedure

All observers are requested to enter the following information in the logbook. Entries areto be made at both opening and closing times. If weather doesn’t allow observing enter asmany items as possible.

Explanation: On the first line for the night the observers name and equipment are to beentered. The following conventions can be used: photometer 1 = single channel; photometer2 = dual channel photometer.

The next two lines are the opening and closing records, respectively. The following explainthe entries.

Opening or closing record:

1. Date – month/day/year

2. EST – Eastern Standard Time

3. Temp – Temperature from thermometer

4. Hum – humidity from dome hygrometer

5. Wind – estimated wind speed

6. % clouds – estimate of percent of cloud cover during night

7. Transp – transparency in clearest regions during observations on scale of 0 mag to 5mag based on apparent magnitude of faintest star visible to naked eye

8. Seeing – estimated mean seeing disk in seconds of arc

9. Hrs. worked – number of hour during which observations were made or attempted

10. Comments – list observing program, problems, or other general remarks you feel appro-priate. Problems should also be reported to the proper individuals the next morning,in a trouble log, and/or to email trouble log trouble@astsun.astro.virginia.edu.

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82

Chapter 9

The Fan Mountain Observatory10-inch Astrograph

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10-inch Astrograph(Rev. August 06, 2007)

1. General Information

The 10-inch Astrograph is located at the Fan Mountain Observatory. It is a wide-fieldcamera for photographing large sections of the sky. Over 900 red dwarf stars have beendiscovered with this instrument. It is currently (2007) being refurbished by members of theCharlottesville Astronomical Society for a joint project with the Astronomy Department.The following procedures may be outdated by the time you read this.

2. Opening procedure

1. Red and white light switches are to the left of the door as you come in.

2. Open dome by hand. Handles are on the shutters.

3. Uncover 10-inch and the finder.

3. Telescope Operation

1. The switches for the drive and the circle lights are mounted on the declination tangentarm.

2. The hand paddle controls the dome movement and RA (right ascension) guide.

3. Declination guide is manual tangent arm.

4. The telescope is clamped in right ascension and declination by hand wheels. Loosenthese wheels and move the telescope by hand. Clamp telescope when you have foundyour field in the finder.

5. In the box on the middle table, you will find a 32mm Brandon eyepiece which is usedfor low power with the finder. Also the focusing eyepiece for the 10-inch is kept here.It is a K25mm.

6. Remove the 12.5mm eyepiece and barlow from the 6-inch finder. (Just let it hang fromthe cord.) Insert the 32mm Brandon eyepiece. This gives about 32 power. (wide field)

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7. Use the 12.5mm eyepiece and barlow for guiding. This eyepiece has a battery controlledreticle.

8. On the top of the Astrograph, there is a Telarod reflex finder. It projects a 1/2◦, 2◦,and 4◦ reticle on the sky. It also is battery operated.

9. Use the K25mm eyepiece with the finding plate located in the tailpiece to locate yourregion in the Astrograph. Hold the eyepiece base against the glass and scan your field.

10. To focus the Astrograph, hold the K25mm eyepiece against the finding plate and lookat a bright star. Focus with the chain wheel.

11. The plate holder is located in the station house darkroom. It is in the second drawerdown to the left.

12. Remove the finding plate from the Astrograph and insert the plate holder in its place.The shutter is the dark slide.

4. Closing Down

1. Turn off drive and circle lights.

2. Return finding plate to the tailpiece.

3. Turn of reticle and the telarod reflex sight.

4. Stow the telescope on the east side of the pier parallel to the floor pointing south.

5. Cover the optics, clamp axis.

6. Close the dome and rotate it to the east (left, if you are in the doorway facing thetelescope).

7. Fill out the log book and turn off lights.

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Chapter 10

The GenI CCD Camera (Imaging)

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The GenI CCD Camera System (Imaging)(Rev. August 17, 2011)

1. System Description

The GenI CCD system uses the Generation I controller developed by San Diego StateUniversity (Leach group) and now managed under the company name of AstronomicalResearch Cameras, Inc. (ARC). The detector is an SI424A scientific grade CCD imagermanufactured by Scientific Imaging Technologies, Inc. (SITe).

The SDSU controller is mounted directly on a CCD liquid nitrogen dewar with a serial fiberoptic communications link leading from the controller housing to a PCI interface card in aSun Ultra5 computer. For operation with the GenI controller, the toggle switch on the backpanel of the computer should be set to “GEN I”.

The power supply for the controller is a box mounted on the east side of the 40-in telescopetailpiece, and the box has a switch which must be turned on for the controller to operate.This power supply is plugged into an AC outlet on the tailpiece which receives power onlywhen the CCD switch on the bottom rack panel in the control room is also turned on. Thecontroller operates an electromechanical shutter mounted inside the tailpiece, either undersoftware control or by way of a toggle switch on a black box near the controller power supply.

The Sun Ultra5 control computer is named crux and uses the Sun Solaris2.8 operatingsystem with the CDE window system. The user interface to the CCD controller is the aprogram called Voodoo developed by SDSU, executed with the command juju, which runs aversion of the program which has been modified locally for use with the GenI controller andCCD on the 40-in telescope at Fan Mountain. Images are stored on disk in FITS (*.fits)format and can be transferred from disk to magnetic tape (4mm DAT DDS4). A typicalfull frame requires 8.6MB of storage. Images can be displayed and analyzed using IRAFtasks. This manual does not explain the details of using IRAF, but IRAF has an extensivebuilt-in help facility, and full documentation is available on the web at the IRAF ProjectHome Page.

2. CCD Camera Specifications

Table 1 summarizes the current configuration of the CCD camera, chip, and dewar

Fig. 1 is a plot of quantum efficiency vs. wavelength for the CCD in the GENI camera.

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Spec ValueDewar IR Labs

liquid nitrogen cooled, 1 ℓ capacityheating resistorhold time ∼ 36 hours

Chip SITe 2048 × 2048 CCD Imagerback-illuminated, thinned to enhance blue response

Operating Temp. unstable above −100◦ Coptimal operating temperature ∼ −110◦ Clowest achievable temperature ∼ −134◦ Ctemperature readout may be erratic

Format 2048 (cols) × 2049 (rows)24 µm square pixels

Field of View 12.5′ × 12.5′

on FMO 1-m 1 pixel = 0.365′′

CTE 0.99998–0.99999Dark Current negligible at −110◦ CFull well > 150, 000 electrons/pixelReadout 85 s for full frame (2049 rows × 2088 columns)

maximum ADU = 65535single amplifier readout modeno on-chip binningno subarray capability

Low Gain Gain: 3.84 e−/ADU, Readout noise: 8.9 e−

High Gain Gain: 2.06 e−/ADU, Readout noise: 16.9 e−

Table 1. Current configuration of the CCD chip and camera.

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Figure 1. Plot of CCD chip quantum efficiency vs. wavelength. The relevantcurve for our chip is the top solid curve.

3. The Dewar

3.1. Description

The CCD is mounted on a cold finger in an evacuated chamber behind a fused silica windowin a liquid nitrogen dewar and is cooled by direct contact of the cold finger with liquidnitrogen. The dewar, manufactured for ARC by Infrared Laboratories, Inc., has a capacityof 1 ℓ and a hold time of about 36 hours. The dewar is capable of cooling the CCD to atemperature as low as about −134◦C, but normally a heating resistor in the dewar is usedto regulate the CCD temperature to some optimal working value between −110◦ and −100◦

C.

A small electric fan with a rotary on/off switch is mounted on the tailpiece of the 40-intelescope to blow warm air through a tube to a connector near the top of the CCD dewar toproduce a continuous flow across the dewar window to prevent fogging. It should normallybe left running constantly while the camera is mounted on the telescope.

3.2. Normal Operation

1. At least 24 hours before your scheduled observing night, send email to Nick Nichols(nichols@astsun.astro.virginia.edu) and ask him to make sure the CCD dewar isfilled and the defogging fan is running. Top off the dewar at the beginning of the night,and again at the end of the night as a courtesy to the next observer if observations arescheduled for the following night.

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2. Filling the dewar takes about 15 minutes if it is still cold from the previous filling, butup to 40 minutes if starting from room temperature in summer. It takes about 4 hoursfor the dewar to cool from room temperature to the optimal operating temperature of−110◦ C, so it is important to allow sufficient time for the cooldown before observing.You should therefore have the dome and catwalk doors open (in order for the air insidethe dome to reach temperature equilibrium with the outside air, which is necessary forgood seeing) and the dewar filled before sunset.

3. To fill the dewar, attach the connector at the end of the hose from a 25ℓ LN2 tankto the CCD dewar and fill the dewar with liquid nitrogen until you see liquid spillingout the side vent of the connector. It takes some time for the hose to cool sufficientlyto allow nitrogen to pass without evaporating, and the connectors will become coatedwith frost. When done filling, unscrew, cover, and stow the fill tube and nitrogen tank.Then attach the spill-tube to the CCD dewar. The spill-tube will prevent nitrogenfrom spilling from the dewar at moderate angles; however, when moving the telescopeto large zenith distances such as when the lens cover is removed or replaced or duringdome flats, nitrogen will still spill out. This is normal, but try to avoid it when thedewar is full. You can avoid some spilling by removing the telescope cover before fillingthe dewar, if conditions permit.

4. To avoid condensation or frost on the dewar window, be sure the defogging fan isrunning.

3.3. Potential Problems and the Dewar Vacuum

As of January 2007 the GenI and GenII CCD dewars have new vacuum valves which sharea single new gauge which can be connected to either dewar. The vacuum is good for severaldays without pumping as long as the dewar is not allowed to warm up. The LN2 hold timeis about 24 hours.

As a routine, keep filling the dewar every 24 hours or so as long as the camera is in useon the telescope. Leave the camera control software up and running on crux to check thetemperature, with temperature regulation set for −110◦C. For the GenI dewar be sure thedefogging fan on the telescope tailpiece is running to keep frost from forming on the dewarwindow. This requires the CCD switch on the rack panel in the control room to be ON, tosupply power to the camera controller and the defogging fan.

The equipment for reading the vacuum gauge can usually be found in the storeroom on thedome floor level, or in the spectrograph room. It consists of a power supply transformerwired up to a 9-pin D connector and a digital multimeter. The D connector should beplugged into the connector on the vacuum gauge (before plugging in the power supply).When the meter is switched on to the 2VDC scale the voltage should ideally read 1.000V,which translates to roughly 0.01µ (0.01mTorr). Every increase of 1V is a factor of 10 inpressure, so 2V would be ∼ 0.1µ, 3V is ∼ 1µ, and 4V is ∼ 10µ. According to the dewarmanual, problems (such as outgassing and difficuly holding LN2) set in when the pressurereaches 5µ, so for our purposes the vacuum is lost if the reading is over 4V. In practice, thedewar will probably not hold LN2 unless the reading is 2.5V or less.

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To pump the dewar, connect the stainless steel hose from the vacuum pump to the dewarflange with a Quick Flange (QF) connector, but leave the dewar valve closed. The seal ismade by compression of an O-ring between mating flanges by finger closure of a wingnut ona metal clamp, and the connectors on the dewar and the pump hose should be kept sealedwith cover flanges when they are not connected to each other.

Plug in the vacuum pump to a 220 VAC outlet, using the extension cord if necessary. Pressthe PUMPING button to turn it on. The vacuum pump is a two-stage pump system whichincludes a controller. The roughing pump operates by itself first. The turbopump shouldspin up automatically when the roughing pump has lowered the pressure far enough forthe turbopump to safely operate. Allow the turbopump to evacuate the hose for at least 30minutes. After that time, if the turbopump is spinning (check the speed indicator if you can’thear it), the pressure should be low enough to safely open the vacuum valve on the dewar.(If the turbopump is not spinning, do not open the dewar vacuum valve! If you cannot finda leak in the hose or fittings that you can repair, the pump may need maintenance.) If thedewar pressure reading is not less than 3V (∼ 1µ) after 3 hours, there is probably a leak ofsome kind which must be fixed before the camera can be used.

When the pressure reading has dropped to 2.5V, close the dewar valve, turn off the vacuumpump, and fill the dewar. Ideally, the dewar will fill completely and the pressure reading willdrop to 1.0V (∼ 0.01µ). If the dewar does not fill completely in less than 20 minutes, let itcool down for an hour or more, check to see that the pressure is still low and pump againif necessary, then try filling it again. As long as the dewar is kept filled and the pressurereading remains less than 2.5V the camera should work properly. When turning off thevacuum pump, wait until all rotor motion has stopped completely before unplugging thecord from the power outlet.

4. Operating the CCD Camera

4.1. Login

1. Log onto crux as user genicam with password juju&u$r.

2. Before proceeding, insert a blank tape into the DAT drive and enter the commandmt -f /dev/rmt/0n status in any terminal window to verify that the tape drive isworking. (Check the label on the tape drive for the device name currently in use.) Youshould get a message resembling:

crux% mt -f /dev/rmt/0n statusSony 4mm DAT tape drive:

sense key(0x6)= Unit Attention residual= 0 retries= 0file no= 0 block no= 0

If you don’t get the above message try power cycling the tape drive. Saving your datato tape is one of the last and most important things you’ll do at the end of the night,so it’s best to make sure this will go smoothly at the outset.

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3. The home directory in which you will be working on crux is /crux/genicam. Inthis directory is the file login.cl, a startup file used by the IRAF program, and thesubdirectory juju, which is used to store setup files for the camera controller.

In addition to the Sun internal 19GB disk, there is also an external 34GB disk attachedto crux which appears as a directory called /data. All raw image files should bestored in the subdirectory /data/genicam. In this directory (i.e. after entering cd/data/genicam), create a unique subdirectory for your images.

4.2. Starting IRAF

First start the DS9 image display program by entering ds9 & at the prompt in a terminalwindow. Then open an xgterm terminal by entering xgterm &. In the xgterm window, fromdirectory /crux/genicam, enter cl to start IRAF. To see a help page for any IRAF task,enter help task at the cl> prompt. One way to run any IRAF task is to enter epar task,edit any parameters that you want to set or change, then type :go and hit RETURN. Taskscan also be run directly from the IRAF command line.

4.3. Starting the Voodoo Program

1. Start the modified version of the Voodoo camera control program by entering thecommand juju in a terminal window. The Voodoo Main window should appear onthe screen (Fig. 2).

2. Some configuration parameters for Voodoo may be set using the popup windowsavailable from the menu bar of the Main window. First select Setup from the menu barto bring up the Setup window (Fig. 3). Load the file /crux/genicam/juju/juju.setupand click Apply to initialize the camera controller, then close the Setup window.

3. The Subarray popup window will not do anything until the necessary readoutinstructions have been added to the code that is downloaded to the processors inthe GenI controller. The Voodoo Focus Sequence will not work either, since it dependson the same subarray readout instructions.

4. Select Parameters from the menu bar to bring up the Controller Parameters window.Select the Temperature tab and set the array temperature control to -110 C (Fig. 4).Click Apply Above and close the Controller Parameters window.

5. Select Debug from the menu bar, then open the Developer Parameters window byselecting Development. Select the Gain tab, set the Low video gain button, then clickApply Above (Fig. 5). Close the Developer Parameters window.

6. If you would like your image headers to contain FITS keywords other than thoserequired for basic formatting, you can use the FITS window (Fig. 6). If TCSLinkis checked, the FITS header parameters labeled Universal Time, Local SiderealTime, Equinox, Airmass, Hour Angle, Right Ascension, and Declination areupdated automatically over a serial link to the telescope control PC at the beginningof each exposure or whenever you click Update. The filter parameters labeled Filter1, Filter 2, Filpos 1, and Filpos 2 will be updated also, regardless of the settingof the TCSLink checkbox. The FITS header parameters with white backgrounds maybe edited manually.

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Figure 2. The Voodoo Main window.

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Figure 3. The Voodoo Setup window.

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Figure 4. The Voodoo Controller Parameters window, Temperature tab.

Figure 5. The Voodoo Developer Parameters window, Gain tab.

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Figure 6. The Voodoo FITS window.

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Figure 7. The Voodoo Filter Control window.

4.4. Filter Control System

The filter wheels inside the telescope tailpiece above the CCD camera shutter can be operatedfrom the filter control panel on the south face of the tailpiece when the switches are set toLOCAL or from the filter PC computer in the control room when the switches are set toREMOTE. Filter wheel A (the lower one, also known as filter wheel 1) has 4 openings spacedat 90◦ intervals and holds 6-in square filters. Filter wheel B (the upper one, also known asfilter wheel 2) has 6 openings spaced at 60◦ intervals and holds 4-in square filters.

To load a filter into a filter wheel, first open the filter wheel access door (the rectangularpanel above the filter control panel held shut by clamps) so you can see the filter wheelsinside the tailpiece. Switch the filter wheel to LOCAL and use the SLEW button on thefilter control panel to rotate it. Open the lock at the edge of the filter opening you select,slide the filter into the slot, then close and gently screw down the lock with your fingers.The filter opening in the telescope light path is the one diametrically opposite the one atthe access door.

A Filter Control window (Fig. 7) has been added to Voodoo to provide an interface to thefilter control system using a serial link between crux and the filter PC.

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1. To control the filter wheels remotely, begin by turning on the filter PC (white tower)underneath the table in the control room. The filter PC boots to a DOS prompt.

2. Enter cd c700\lotion at the DOS prompt to get to the correct directory. Then enterpotion to start the version of the filter control program that operates with Voodoo.

3. The filter PC first checks for initialization:

Assuming filter wheel positions 1,1 to start.

If not, set positions on LOCAL ("GO HOME" buttons).

Enter "Y" when ready to start.

If necessary, go upstairs to the dome and HOME both filter wheels under LOCALcontrol. This sets filter positions 1,1 (filter openings numbered “1” in the telescopelight path). Then switch both wheels back to REMOTE and go back down to thecontrol room.

4. Now click Init in the Voodoo Filter Control window. This must be done to initializethe filter wheel positions to 1,1 in the Voodoo software.

5. To move the filter wheels, select the desired Filter Wheel position numbers withthe radio buttons, then click Move. Voodoo calculates the necessary moves, sendscommands to the filter PC, and updates the Filter Control display. Although theupdates appear immediately in Voodoo, the filter PC monitor displays the actual movecommand while it is being executed and gives a confirmation when it is done.

6. The numerical filter positions and the corresponding descriptive labels in the text fieldsin the Filter Control window are always updated automatically in the Filter Controlwindow and included as FITS header parameters FILPOS1, FILPOS2, FILTER1, andFILTER2. The descriptive labels may be edited to match the filters loaded in the wheels,and these configurations may be saved and loaded as filter setup files with extension*.flt using the Load and Save buttons.

7. The Home button moves the filter wheels to the initialized position 1,1.

8. The Exit button causes the filter PC program to quit.

4.5. Scope Control System

A Scope Control window (Fig. 8) has been added to Voodoo to allow the user to load anobject list and command the telescope to slew to a selected list object using the serial linkto the telescope control PC.

An object list must be a simple text file with extension *.lst, with one line per object. Theformat of each object line is arbitrary and may include any number of fields of any reasonablelength, except that each line must include the RA and DEC separated by whitespace (spacesor tabs) only, each in sexagesimal format with no whitespace padding.

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Figure 8. The Voodoo Scope Control window.

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1. In the Voodoo Scope Control window, click Load to select and load an object list file.

2. Enter the Equinox of the coordinate list in the Equinox text field. This must be doneonly once per loaded list and may be changed at any time.

3. To slew the telescope to a list object, swipe the coordinate section of the object linewith the mouse (RA and DEC fields together) so that it is highlighted, then click Slew.The slew commmand will be echoed in the main Voodoo Information Window and theTCS will immediately slew the telescope. As always, a slew can be aborted with theStop slew command (8) from the TCS Movement menu.

4. Object lists cannot be edited or saved from the Scope Control window.

4.6. Taking an Exposure

1. Check Save to Disk in the Main window and enter the full pathname of your imagedirectory and a beginning filename for your images. If Auto Incr is checked, thenumeric part of the filename will be automatically incremented with each new exposure.Otherwise you must enter a new filename for each new image.

2. For normal exposures, check Open Shutter, enter the desired exposure time, and clickExpose in the Main window.

3. Display and analyze the images with IRAF and DS9.

4.7. Ending a CCD Session

1. To copy your image files to DAT tape, change to your image directory in any teminalwindow, then use the unix command

tar cvf /dev/rmt/0n .

to write all your image files to tape. (This takes about half an hour for 100 images.)

2. After your images have been written to tape, rewind the tape and take the tape drive offline by entering mt -f /dev/rmt/0 rewoffl, then remove your tape from the drive.

3. Exit Voodoo (remember to home the filter wheels and exit the filter control systemfrom the Filter Control window first), log out of IRAF, quit DS9, exit xgterm, and logout of the CDE window system.

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Chapter 11

The GenII CCD Camera(Spectroscopy)

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104

The GenII CCD Camera System (Spectroscopy)(Rev. August 17, 2011)

1. System Description

The GenII CCD system uses the Generation II controller developed by San Diego State

University (Leach group) and now managed under the company name of Astronomical

Research Cameras, Inc. (ARC). The detector is an SI424A scientific grade CCD imager

manufactured by Scientific Imaging Technologies, Inc. (SITe). This camera system is

intended primarily use with the Fan Mountain Observatory Bench Spectrograph (FMOBS),

which is described in detail elsewhere.

The SDSU controller is mounted directly on a CCD liquid nitrogen dewar with a serial fiber

optic communications link leading from the controller housing to a PCI interface card in a

Sun Ultra5 computer. For operation with the GenII controller, the toggle switch on the back

panel of the computer should be set to “GEN II”.

The power supply for the controller is a gray metal box with a switch which must be turned

on for the controller to operate. Other hardware details of the system will depend on the

spectrograph setup.

The Sun Ultra5 control computer is named crux and uses the Sun Solaris2.8 operating system

with the CDE window system. The user interface to the CCD controller is a program called

Voodoo developed by SDSU and modified locally for use at Fan Mountain. Images are stored

on disk in FITS (*.fits) format and can be transferred from disk to magnetic tape (4mm

DAT DDS4). A typical full frame requires 8.6MB of storage. Images can be displayed and

analyzed using IRAF tasks. This manual does not explain the details of using IRAF, but

IRAF has an extensive built-in help facility, and full documentation is available on the web

at the IRAF Project Home Page.

2. CCD Camera Specifications

Table 1 summarizes the current configuration of the CCD camera, chip, and dewar.

Fig. 1 is a plot of quantum efficiency vs. wavelength for the CCD in the GENII camera.

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Spec ValueDewar IR Labs

liquid nitrogen cooled, 1 ℓ capacityheating resistorhold time ∼ 36 hours

Chip SITe 2048 × 2048 CCD Imagerback-illuminated, thinned to enhance blue response

Operating Temp. unstable above −100◦ Coptimal operating temperature ∼ −110◦ Clowest achievable temperature ∼ −134◦ C

Format 2048 (cols) × 2049 (rows)24 µm square pixels

CTE 0.99998–0.99999Dark Current negligible at −110◦ CFull well > 150, 000 electrons/pixelReadout maximum ADU = 65535

4 available readout amplifiers (A,B,C,D)single, dual, or quad readoutconfigurable subarray readout capability

Low Gain (C1S) Amp C, Gain Set 1.0, Slow Integrate, No MPPBias 3989 ADU, Gain 6.1 e− ADU−1, Read Noise 4.5 e−

High Gain (C2S) Amp C, Gain Set 2.0, Slow Integrate, No MPPBias 1237 ADU, Gain 2.8 e− ADU−1, Read Noise 7.8 e−

Table 1. Current configuration of the CCD chip and camera.

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Figure 1. Plot of CCD chip quantum efficiency vs. wavelength. The relevantcurve for our chip is the top solid curve.

3. The Dewar

3.1. Description

The CCD is mounted on a cold finger in an evacuated chamber behind a fused silica windowin a liquid nitrogen dewar and is cooled by direct contact of the cold finger with liquidnitrogen. The dewar, manufactured for ARC by Infrared Laboratories, Inc., has a capacityof 1 ℓ and a hold time of about 36 hours. The dewar is capable of cooling the CCD to atemperature as low as about −134◦C, but normally a heating resistor in the dewar is usedto regulate the CCD temperature to some optimal working value between −110◦ and −100◦

C.

3.2. Normal Operation

1. At least 24 hours before your scheduled observing night, send email to Nick Nichols(nichols@astsun.astro.virginia.edu) and ask him to make sure the CCD dewaris filled. Top off the dewar at the beginning of the night, and again at the end of thenight as a courtesy to the next observer if observations are scheduled for the followingnight.

2. Filling the dewar takes about 15 minutes if it is still cold from the previous filling, butup to 40 minutes if starting from room temperature. It takes about 4 hours for thedewar to cool from room temperature to the optimal operating temperature of −110◦

C, so it is important to allow sufficient time for the cooldown before observing.

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3. To fill the dewar, attach the connector at the end of the hose from the dewar to a 25ℓLN2 tank and fill the dewar with liquid nitrogen until you see liquid spilling out theside vent of the dewar connector. It takes some time for the hose to cool sufficientlyto allow nitrogen to pass without evaporating, and the connectors will become coatedwith frost.

3.3. Potential Problems and the Dewar Vacuum

As of January 2007 the GenI and GenII CCD dewars have new vacuum valves which sharea single new gauge which can be connected to either dewar. The vacuum is good for severaldays without pumping as long as the dewar is not allowed to warm up. The LN2 hold timeis about 24 hours.

As a routine, keep filling the dewar every 24 hours or so as long as the camera is in useon the telescope. Leave the camera control software up and running on crux to check thetemperature, with temperature regulation set for −110◦C. (For the GenI dewar be sure thedefogging fan on the telescope tailpiece is running to keep frost from forming on the dewarwindow. This requires the CCD switch on the rack panel in the control room to be ON, tosupply power to the camera controller and the defogging fan.)

The equipment for reading the vacuum gauge can usually be found in the storeroom on thedome floor level, or in the spectrograph room. It consists of a power supply transformerwired up to a 9-pin D connector and a digital multimeter. The D connector should beplugged into the connector on the vacuum gauge (before plugging in the power supply).When the meter is switched on to the 2VDC scale the voltage should ideally read 1.000V,which translates to roughly 0.01µ (0.01mTorr). Every increase of 1V is a factor of 10 inpressure, so 2V would be ∼ 0.1µ, 3V is ∼ 1µ, and 4V is ∼ 10µ. According to the dewarmanual, problems (such as outgassing and difficuly holding LN2) set in when the pressurereaches 5µ, so for our purposes the vacuum is lost if the reading is over 4V. In practice, thedewar will probably not hold LN2 unless the reading is 2.5V or less.

To pump the dewar, connect the stainless steel hose from the vacuum pump to the dewarflange with a Quick Flange (QF) connector, but leave the dewar valve closed. The seal ismade by compression of an O-ring between mating flanges by finger closure of a wingnut ona metal clamp, and the connectors on the dewar and the pump hose should be kept sealedwith cover flanges when they are not connected to each other.

Plug in the vacuum pump to a 220 VAC outlet, using the extension cord if necessary. Pressthe PUMPING button to turn it on. The vacuum pump is a two-stage pump system whichincludes a controller. The roughing pump operates by itself first. The turbopump shouldspin up automatically when the roughing pump has lowered the pressure far enough forthe turbopump to safely operate. Allow the turbopump to evacuate the hose for at least 30minutes. After that time, if the turbopump is spinning (check the speed indicator if you can’thear it), the pressure should be low enough to safely open the vacuum valve on the dewar.(If the turbopump is not spinning, do not open the dewar vacuum valve! If you cannot finda leak in the hose or fittings that you can repair, the pump may need maintenance.) If the

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dewar pressure reading is not less than 3V (∼ 1µ) after 3 hours, there is probably a leak ofsome kind which must be fixed before the camera can be used.

When the pressure reading has dropped to 2.5V, close the dewar valve, turn off the vacuumpump, and fill the dewar. Ideally, the dewar will fill completely and the pressure reading willdrop to 1.0V (∼ 0.01µ). If the dewar does not fill completely in less than 20 minutes, let itcool down for an hour or more, check to see that the pressure is still low and pump againif necessary, then try filling it again. As long as the dewar is kept filled and the pressurereading remains less than 2.5V the camera should work properly. When turning off thevacuum pump, wait until all rotor motion has stopped completely before unplugging thecord from the power outlet.

4. Operating the CCD Camera

4.1. Login

1. Log onto crux as user bench with password me4bench.

2. Before proceeding, insert a blank tape into the DAT drive and enter the commandmt -f /dev/rmt/0n status in any terminal window to verify that the tape drive isworking. (Check the label on the tape drive for the device name currently in use.) Youshould get a message resembling:

crux% mt -f /dev/rmt/0n status

Sony 4mm DAT tape drive:

sense key(0x6)= Unit Attention residual= 0 retries= 0

file no= 0 block no= 0

If you don’t get the above message try power cycling the tape drive. Saving your datato tape is one of the last and most important things you’ll do at the end of the night,so it’s best to make sure this will go smoothly at the outset.

3. The home directory in which you will be working on crux is /crux/bench. In thisdirectory are the directories fobos, which may be used to store setup files for thecamera controller, and iraf, which contains the file login.cl, a startup file used bythe IRAF program.

In addition to the Sun internal 19GB disk, there is also an external 34GB disk attachedto crux which appears as a directory called /data. All raw image files should bestored in the subdirectory /data/bench. In this directory (i.e. after entering cd

/data/bench), create a unique subdirectory for your images.

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4.2. Starting IRAF

First start the DS9 image display program by entering ds9 & at the prompt in a terminalwindow. Then open an xgterm terminal by entering xgterm &. In the xgterm window, fromdirectory /crux/bench/iraf, enter cl to start IRAF. To see a help page for any IRAF task,enter help task at the cl> prompt. One way to run any IRAF task is to enter epar task,edit any parameters that you want to set or change, then type :go and hit RETURN. Taskscan also be run directly from the IRAF command line.

4.3. Starting the Voodoo Program

1. Start the Voodoo camera control progam by selecting the Voodoo icon from the Gnomecontrol panel. The Voodoo Main window (Fig. 2) should appear on the screen.

2. Many configuration parameters for Voodoo may be set using the popup windowsavailable from the menu bar of the Main window. First select Setup from the menu barto bring up the Setup window (Fig. 3). Load the file /crux/bench/fobos/C1S.setup

for Low Gain or the file /crux/bench/fobos/C2S.setup for High Gain, and click Applyto initialize the camera controller, then close the Setup window.

3. Select Parameters from the menu bar to bring up the Controller Parameters window.Select the Temperature tab, set the array temperature control to -110.0 C, and clickApply Above (Fig. 4). Select the Readout tab, choose Amplifier C, for example, andclick Apply Above (Fig. 5). This currently seems to be the best readout amplifier forgeneral purposes. Close the Controller Parameters window.

4. Select Debug from the menu bar, then open the Developer Parameters window byselecting Development. Select the Gain tab and set, for example, Video Gain 1.0 andIntegrator Speed Slow, then click Apply Above (Fig. 6). Close the Developer Parameterswindow.

5. Select Subarray from the menu bar to bring up the Subarray window and configure thesubarray as desired. See Fig. 7 for an example. Click Apply to apply the settings. Torevert to Full Array operation, select Full Array and click Apply. Close the Subarraywindow.

6. If you would like your image headers to contain FITS keywords other than thoserequired for basic formatting, you can use the FITS window (Fig. 8). If TCSLinkis checked, the FITS header parameters labeled Universal Time, Local Sidereal

Time, Equinox, Airmass, Hour Angle, Right Ascension, and Declination areupdated automatically over a serial link to the telescope control PC at the beginningof each exposure or whenever you click Update. The FITS header parameters withwhite backgrounds may also be edited manually.

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Figure 2. The Voodoo Main window.

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Figure 3. The Voodoo Setup window.

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Figure 4. The Voodoo Controller Parameters window, Temperature tab.

Figure 5. The Voodoo Parameters window, Readout tab.

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Figure 6. The Voodoo Developer Parameters window, Gain tab.

Figure 7. The Voodoo Subarray window.

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Figure 8. The Voodoo FITS window.

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Figure 9. The Voodoo Scope Control window.

4.4. Scope Control System

A Scope Control window (Fig. 9) has been added to Voodoo to allow the user to load anobject list and command the telescope to slew to a selected list object using the serial linkto the telescope control PC.

An object list must be a simple text file with extension *.lst, with one line per object. Theformat of each object line is arbitrary and may include any number of fields of any reasonablelength, except that each line must include the RA and DEC separated by whitespace (spacesor tabs) only, each in sexagesimal format with no whitespace padding.

1. In the Voodoo Scope Control window, click Load to select and load an object list file.

2. Enter the Equinox of the coordinate list in the Equinox text field. This must be doneonly once per loaded list and may be changed at any time.

3. To slew the telescope to a list object, swipe the coordinate section of the object linewith the mouse (RA and DEC fields together) so that it is highlighted, then click Slew.The slew commmand will be echoed in the main Voodoo Information Window and the

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TCS will immediately slew the telescope. As always, a slew can be aborted with theStop slew command (8) from the TCS Movement menu.

4. Object lists cannot be edited or saved from the Scope Control window.

4.5. Taking an Exposure

1. Check Save to Disk in the Main window and enter the full pathname of your imagedirectory and a beginning filename for your images. If Auto Incr is checked, thenumeric part of the filename will be automatically incremented with each new exposure.Otherwise you must enter a new filename for each new image.

2. For normal exposures, check Open Shutter, enter the desired exposure time, and clickExpose in the Main window.

3. Display and analyze the images with IRAF and DS9.

4.6. Ending a CCD Session

1. To copy your image files to DAT tape, change to your image directory in any teminalwindow, then use the unix command

tar cvf /dev/rmt/0n .

to write all your image files to tape. (This takes about half an hour for 100 images.)

2. After your images have been written to tape, rewind the tape and take the tape driveoff line by entering mt -f /dev/rmt/0 rewoffl, then remove your tape from the drive.Exit Voodoo, log out of IRAF, quit DS9, exit xgterm, and log out of the CDE windowsystem.

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118

Chapter 12

The Fan Observatory Bench OpticalSpectrograph (FOBOS)

119

120

Fan Observatory Bench Optical Spectrograph(FOBOS)

(Rev. August 06, 2007)

The Fan Observatory Bench Optical Spectrograph (FOBOS) is a fiber–fed,

bench–mounted, single–object spectrograph. The instrument is designed to

observe point sources at moderate resolution to V ∼ 14, although extended

objects can also be observed if knowledge of the precise spatial sampling is not

important.

This manual is intended for the observer and gives the information required to

operate the instrument night to night. Although the intention is to instruct

a true beginner, reading the manual is absolutely no substitute for hands-on

training. NO PERSON should attempt to use the instrument for the first time

without having an experienced observer present for supervision. Ideally, anyone

interested in using the instrument should accompany an experienced observer for

at least one night prior to observing on their own. Additional detailed technical

information can be found in the “FOBOS Technical Reference”, in Jeff Crane’s

dissertation, and in the FOBOS primary reference publication (PASP, 2005, 117,

526).

Please e-mail Jeff with any suggestions concerning this manual or the instrument

itself.

Contact Phone E-mail Role

Jeff Crane . . . crane@ociw.edu Instrument DesignerSteve Majewski 924-4893 srm4n@virginia.edu Principal InvestigatorDavid McDavid 924-4899 dam3ma@virginia.edu 40” & Instrument SupportRicky Patterson 924-4914 rjp0i@virginia.edu Co-Investigator

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1. Instrument Overview

FOBOS is operated from the 40” Control Room on the third floor of the observatory. Partsof the instrument itself are located on all four floors of the building. FOBOS can be brokenup into three main components: the Focal Plane Module, the Fiber Train, and the BenchSpectrograph itself (See Figure 1).

Tailpieceand

Focal PlaneModule

SpectrographEnclosure

BenchSpectrographPier

Telescope

TrainFiber

TelescopeFMO 40"

Figure 1. The complete FOBOS system is shown on the 1-meter telescope. Thebuilding and telescope pier are shown in cross-section. The fiber train runs fromthe Focal Plane Module through the telescope’s polar axis (not shown) and downthe side of the telescope pier to the Bench Spectrograph enclosure.

1.1. The Focal Plane Module

The Focal Plane Module (Figure 2) mounts to the base of the telescope tailpiece at theCassegrain focus. Its functions include:

• Providing a mechanism for target/fiber alignment

• Providing calibration light for the spectrograph

A movable fold mirror carriage just above the telescope’s focal plane enables three separateoptical paths:

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Figure 2. Diagram of the Focal Plane Module, viewed from the West side.

• Primary (coarse) Acquisition: The telescope image plane is demagnified 5× and viewed

by an SBIG STV video camera, yielding a 6.0×4.4 arcmin field of view. The target

star can be viewed, identified, and roughly positioned on the fiber of choice. The

approximate poisition of the preferred fiber (Fiber 1, positioned along the telescope’s

optical axis) is marked on the video monitor in the control room.

• Secondary (fine) Acquisition: Telescope light comes into focus in the plane of the

fiber ferrules. The guide fibers (see section 1.2.) are monitored with a second SBIG

STV camera while the alignment of the target star is fine-tuned. When alignment

is achieved, the telescope autoguider may be engaged if necessary, and observing can

begin.

• Calibration: Three arc lamps and a quartz-tungsten-halogen (QTH) lamp are available

for calibrations. These lamps illuminate an opal diffusing glass, which in turn is imaged

onto the plane of the Focal Plane Ferrules. Calibration light is then transmitted to the

Bench Spectrograph.

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Guide Fibers

Science Fiber

Stainless SteelCapillary Tube

Teflon TubingAttachment

Figure 3. The focal plane fiber ferrule is shown in isometric projection in full andin cross-section. The teflon tube–encased fibers enter at the base where the teflontubes are epoxied to the aluminum. The fibers themselves are then brought to aclose–packed hexagonal array in the capillary tube extension.

1.2. The Fiber Train

The main length of the fiber train consists of 7 (redundant) “science fibers” that transmitlight from the telescope to the Bench Spectrograph. In the telescope’s focal plane, eachscience fiber is mounted in a ferrule (Figure 3) and surrounded closely by 6 short guidefibers, which can be used for fine-tuning the target alignment. Although there are severalfibers that run from the telescope’s focal plane to the bench spectrograph, only one fibermay be used at a time to collect light from a target. The fibers are fixed and cannot beindependently positioned. At present, only five of the seven science fibers are functional, andonly two are optimized for observation of science targets; the remaining three are intendedfor collection of diffuse background (sky) emission for subtraction during data processing.

At the telescope level, power and communication cables are tethered to the fiber train asit drapes from the Focal Plane Module to the fork of the telescope (Figure 4). When theFocal Plane Module is attached to the telescope’s tailpiece, the fiber train should always beattached to the left arm of the telescope fork using the eyebolts in the fork and snap hooksattached to the fiber train. When the Focal Plane Module is not in use, it should be parkedon its lift system to the left of the fork and the fiber train should be detached from the foureyebolts.

It is VERY important to make sure that while slewing the telescope, the fibertrain does not catch on any foreign objects, including the tailpiece or hardwareattached to the telescope. Constructing the fiber train took several hundred hours ofwork, and great care should be taken to make sure it does not become damaged.

1.3. The Bench Spectrograph

The Bench Spectrograph (Figure 5) sits on a vibrationally isolated optical table in a stable,environmentally controlled enclosure.

The Fiber Train attaches to the Science Fiber Mount (Figure 6), where the science fibersare arranged in a linear, vertical array. By default, the fiber ends themselves define the

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TelescopeFork

Fiber Train Focal PlaneModule

Control Box

Focal PlaneModule

STV controlboxes

Figure 4. The Focal Plane Module is shown attached to the 40” tailpiece. TheFiber Train drapes freely to the left side of the telescope’s fork, where it attachesto eye bolts using snap hooks. When the spectrograph is unmounted, the FiberTrain should be detached from the fork.

“entrance slit”. However, immediately in front of the ferrules is positioned a slot for anoptional entrance slit mask. Following the slit position, there are two slots for optionalinterference filters and an opal glass used for making “milky flats”. The instrument’s shutteris attached to the front of the Science Fiber Mount.

The Collimator Mount holds a 100mm diameter, 350mm focal length achromatic doublet lensand an iris diaphragm. The focus of the collimator and iris diameter should not normallyneed to be adjusted by the observer during an observing run.

The Grating Mount contains a rotation stage that can hold one reflection grating from theinventory at a time. The primary setup 1 calls for a 100×100mm grating with 1200 lines/mmblazed for 6000A.

The Dewar Mount rides on a linear rail that pivots directly under the diffraction grating’sreflective surface. A 135mm f/2 SLR lens on the front of the Dewar Mount focuses diffractedlight onto the CCD. The SLR lens front focus should always be set to ∞. The rear focus,once set by technical staff, should not be adjusted. The azimuthal rotation of the CCD withrespect to the optical axis of the SLR lens may be adjusted using the micrometer on the

1Throughout this manual, reference will be made to the “primary” setup, which is the instrument configurationdesigned for use by the Grid Giant Star Survey (GGSS): 4700–6700A coverage at R ∼ 1200.

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CCD dewarCCD power supply

Collimator Mount

Scie

nce

FIbe

r M

ount

SLR

lens

Gra

ting

Mou

ntG

ratin

g co

ver

Fibe

r T

rain

SLR cover Celestron telescope

Dewar Mount

Figure 5. The Bench Spectrograph is shown from overhead. The fiber trainattaches to the Science Fiber Mount assembly on the right. The CCD and camerarotate on a pivot arm (not visible in this view) to allow a range of collimator-grating-camera angles. The Celestron telescope is used by technical staff to focusthe collimator.

top of the mount. This may be necessary to align the spectra along rows of the CCD. Theazimuthal rotation of the CCD with respect to the optical table may be adjusted using amicrometer on the rear of the Dewar Mount. This may be necessary to account for tilt inthe focal plane, but should not be adjusted after the start of a run.

The detector is a 2048×2048 SITe CCD with 24 µm square pixels operated by an SDSUCCD Laboratory (Bob Leach) Generation II controller. Note that because of non-symmetricvignetting on the red side of the chip, the full 2048 columns are not actually illuminated.The actual usable portion of the spectra will cover something like 1850-1900 pixels, and thequoted wavelength coverage will drop by an equivalent amount.

2. Available Configurations

FOBOS was designed to collect moderate resolution spectra of candidate K giants for theGrid Giant Star Survey. Spectra collected for this project in the Southern hemisphere coverthe region ∼4700–6700 A with ∼1 A/pixel dispersion. To match these spectra, one diffractiongrating was chosen for work in first order with no interference filter necessary.

As the instrument’s usability is demonstrated, additional diffraction gratings, interferencefilters, and optional slit masks may be added to the inventory to allow a variety of different

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FiberTrain

Slit maskor dummyFilter Slot #1Filter Slot #2

Shutter Slit positionercover

Science fiberarray handle

Filter/Slitremoval tool

Figure 6. Science Fiber Mount shown from above with top cover removed.

configurations capable of covering the full optical wavelength range. As the inventorychanges, this section will be expanded to more fully describe the various configurationsavailable to observers.

Grating Lines/mm Blaze δ Blaze λ Ruled area

1200@157 1200 15.7◦ 4500 A 100×100 mm1200@211 1200 21.1◦ 6000 A 100×100 mm1200@267 1200 26.7◦ 7500 A 154×128 mm

Table 1. FOBOS diffraction grating inventory.

Filter Shape Width Thickness

GG-420 square 25.4 mm 3 mmRG-610 round 25.4 mm 3 mmOpal square 25.4 mm 3 mm

Table 2. FOBOS filter inventory.

3. Setting Up

Please take care to keep the spectrograph room clean. Do not eat, drink, or smokein the room. Every time you enter, clean the soles of your shoes by planting your feet firmlyon the sticky mat in the entryway. If the mat does not feel sticky, step on a different area.When no sticky surfaces remain, peel off and dispose the top layer of the mat.

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Figure 7. Total transmission through the interference filters.

Slit Width Throughput

None 200 µm 100%1 100 µm 60.8%

Table 3. FOBOS slit mask inventory.

3.1. Filling the Dewar

Standard safe handling procedures should be followed when working with liquid Nitrogen.In the spectrograph room, roll the 25-liter dewar to the end of the optical table nearestthe storage area. Insert the “stinger” into the CCD dewar’s fill tube. Tighten thethreaded connector with the spill vent pointing toward the wall and away from thespectrograph optics. Fill the CCD dewar until ℓN2 begins to spill out of the connector’sside vent. This will probably take about 10 minutes if the dewar is already cool. Allow thehose to thaw until flexible before removing the stinger — otherwise you’re likely to breakthe fill hose in two!

3.2. Enabling the Vibration Isolator

The Bench Spectrograph’s optical table is mounted on a pneumatic vibration isolator.This provides some dampening of vibrations in the floor that would otherwise translateto vibrations in the optics on the table.

To enable the system, first make sure that the isolator’s air tube is attached to the aircompressor’s air hose dangling from the ceiling of the spectrograph room. Insert the plastic

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air tube firmly into the brass and red plastic fitting on the end of the thick black aircompressor hose. On the ground floor of the observatory next to the the telescope’s supportcolumn, find the air compressor. Make sure that the water drain valve on the bottom of theair tank is closed. Also make sure the regulator is closed (turned fully clockwise). Turn theOFF/AUTO lever to AUTO and let the tank’s pressure build. The internal pressure should buildto about 125 psi before the compressor will turn off. Now open the regulator to pressurizethe hose leading to the spectrograph room to about 60 psi.

Return to the spectrograph room and make sure that the optical table has been elevatedabout 3/8”. If the lift distance varies greatly from 3/8” the pressurizing or adjustmentscrews on the leveling arms of the isolator may need to be adjusted. Listen for air leaks inthe supply line connection. If you hear one, you may need to tighten the connection.

3.3. Preparing the Spectrograph Room

Turn off the air conditioner and close and clamp the A/C door (Figure 8). Turn off the aircleaner and the dehumidifier. Turn on the power switch to the CCD (gray box next to thedewar on the optical table) if it is not already on. Grab a flashlight. Turn off the lights.Carefully remove the cover of the SLR lens on the front of the CCD dewar. Be careful not torotate the SLR lens itself; the front focus of the SLR lens should always be set to ∞. Verycarefully remove the grating cover and set it aside. Be very, very careful not to touchthe diffraction grating. The grating cost several thousand dollars and cannotbe cleaned! If you touch it, it will have your greasy fingerprints on it for theremainder of its lifetime. When you exit the room, turn off the light and pull both doorsfirmly closed behind you.

3.4. Computer Start-up

Follow the standard start-up procedure for powering on the telescope and tailpiece. Turnon the Dell autoguider PC, making sure that the keyboard/monitor switch is turned to thecorrect position. Once the computer comes up, flip the monitor/keyboard switch and turnon the TCS computer. Start TCS. Turn on the CCTV monitors for the autoguider STV,dome camera, and FOBOS STVs. Turn on the FOBOS PC. Power on the Sun workstationnamed crux. Log in as user bench. Contact one of the people listed on the front of thismanual or a previous FOBOS observer to get the account password. Start the VoodooCCD control software (see documentation for the GenII CCD camera), DS9, and IRAF inan xgterm. If it’s not already on, turn on the FMO EMCS (Environment Monitoring andControl System) PC and start the EMS software.

After the dome room has been prepared (Section 3.5.), establish a connection with theautoguider STV on the Autoguider PC, and with the two FOBOS STVs on the FOBOS PC.The FOBOS coarse acquisition STV communicates with the PC through the COM1 portwhile the Guide Fiber STV communicates through the COM2 port.

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Air conditioner

Air cleaner

A/C door

Dehumidifier

Figure 8. The back right corner of the spectrograph room. Environmental controldevices should be turned off at dusk prior to observing, and the air conditioner framedoor should be closed and latched. During the day when observing is not takingplace, all environmental control devices should be turned on again.

3.5. Preparing the Dome Room

Around sunset, prop the doors to the catwalk open. Open the dome slit and detach the

power cord from the dome. Turn on the telescope tube fans if they are not already on.

Check the fiber train to make sure that it is hanging properly. It should be attached to

the left arm of the fork in several places, almost all the way to the telescope’s declination

axis. Slew the telescope to the north and remove the cover. Remove the cover of the 8”

autoguider telescope and send the telescope to zenith again. Turn on the power to the

telescope autoguider STV control box on. Make sure that the power to the spectrograph’s

two STV cameras and the electronics control box is on. The power strip attached to the right

(West) side of the primary mirror cell should be on as should the power switches on the STV

control boxes. Note that the “CCD” power switch at the bottom of the electronics rack in the

control room must be turned on before power can be supplied to the Focal Plane Module and

STV cameras. Make sure the spectrograph’s electronics control is set to “remote”. Open the

in-tailpiece shutter using the switch near the back left side of the primary mirror cell. Turn

off the air conditioner power on the left wall of the dome room. Set the humidistat-controlled

heat lamps to the off position. Turn off the lights and shut the door to the dome room on

your way out.

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STV MonitorAutoguider

MonitorFMOEMCSTCSTailpiece

Filter Control

peripheralscrux

crux CPU

crux Monitor

crux power

PC

Monitor

IntercomMonitorswitch

Autoguider/TCS Autoguider/TCSPaddle

FOBOSMonitorFOBOS

PaddleTelescope

STV MonitorFOBOS

STV switchFOBOS

FMOEMCS

ControlMotor

PowerInstrument

Telescope

TCS PC

PCFOBOS

Figure 9. The 40” control center. All but the filter wheel control PC are usedduring operation of the spectrograph.

3.6. Please please please...

Don’t touch the surface of diffraction grating, SLR lens glass, or collimator glass.

Don’t crush, yank, or tightly bend the PVC pipe containing the fiber optics.The fleas of a thousand rabid camels will be set upon your carcass if you breakthe fiber optics.

4. Observing

4.1. What Data Should You Collect?

For any scientific target, it’s a good idea to split up your observations into three separateexposures to be combined later. This simplifies cosmic ray removal.

To adequately calibrate your spectra, you will want to take the following additional data:

• Bias frames. Take at least one set of bias frames (zero second exposures) each night.A good rule of thumb is to take 10 frames and then median combine them later.

• Milky flats. During the evening before observing, insert the opal glass in Slot 2 in theScience Fiber Mount on the optical bench. Be sure to replace the cover on the mount.

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Move the fold mirror array in the Focal Plane Module to the Calib position and turnon the quartz (QTH) lamp. Take a few exposures of a few thousand counts each. Inthe primary setup, exposure lengths of about 5 minutes should suffice. These can bemedian combined later to produce a flat field image. You can also use the daytime skyto produce milky flats. Although the required integration times will be longer for thedaytime sky, the resulting flats may be more evenly illuminated. Remember to removethe opal glass and replace the mount cover when you are finished!

• Quartz lamp exposures. The quartz lamp spectra are bright continua that can be usedto estimate fiber-to-fiber relative throughput differences and to determine referencetraces for extracting faint object and arc lamp spectra. With the Focal Plane Module’sfold mirror carriage in the Calib position, turn on the quartz (QTH) lamp. 1 secondexposures should suffice. Ideally, the spectrograph should be stable enough that onlya single QTH lamp exposure per night is required. However, until the instrumentstability has been verified, it’s a good idea to take several throughout the night. Notethat for the determination of relative fiber throughput, daytime sky (solar) spectra willbe more accurate.

• Solar spectra. In addition to being useful wavelength calibration spectra, observationsof the daytime sky will provide more accurate determinations of the relative through-puts of the various fibers during data reduction. The calibration lamp system doesnot illuminate each science fiber completely evenly. If the relative fiber throughput isimportant to you (as it should be if you want accurate sky subtraction), observations ofthe daytime sky (solar spectrum) will be useful. These would then replace the Quartzlamp exposures.

• Camparison (arc lamp) exposures. Three independent comparison sources areavailable: Neon (Ne), Argon (Ar), and Xenon (Xe). Depending on your instrumentsetup, some lamp(s) may be more useful than others. In the primary setup, it appearsthat a 60-second exposure suffices, with the Ne lamp turned on for a fraction of asecond (it is much brighter than the others). To accomplish this, turn on all threelamps, set the CCD exposure time at 60 seconds, and start the exposure. When youhear the shutter open through the intercom, immediately turn off the Ne lamp. Again,given good instrument stability, only one comparison lamp exposure per night shouldbe necessary, but it is advised that multiple exposures be taken throughout the nightuntil confidence in the stability has been established.

• Radial velocity standards. If you’re doing radial velocity work, you will want to observesome number of radial velocity standards for comparison later. A good list is providedin the Astronomical Almanac.

• Flux standards. If you are doing work where the absolute flux of the star, or therelative flux between lines are required, you will want to observe flux standards so thatthe instrumental, wavelength-dependent efficiency profile can be removed. Multipleliterature references are available for selecting flux standards, one of which is:Massey, Strobel, Barnes, and Anderson, 1988, ApJ, 328, 315.

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4.2. Spectrograph Control System

During normal observing, the user will need to control the Focal Plane Module fold mirrorcarriage, wavelength calibration lamps, quartz lamp, coarse and fine acquisition cameras,autoguider camera and telescope, 40” telescope, and SITe CCD.

The fold mirror carriage and calibration lamps may be controlled either by using theelectronics control panel attached to the Focal Plane Module or by using the remote paddlein the control room (Figure 9). A Local/Remote switch on the control panel determineswhich location has control. In both places may be found ON/OFF switches for each ofthe four calibration lamps (QTH, Ne, Ar, Xe) and three push buttons that send the mirrorcarriage to its three available positions.

The three carriage positions are labeled Calib, Observe, and Acquire. In the Calib position,a fold mirror enables the calibration lamp system. In the Observe position, the focal planeferrules are exposed to light from the telescope. If a target is aligned on the end of a ferrule,light will find its way to the Guide Fiber STV camera and Bench Spectrograph. In theAcquire position, a fold mirror enables the primary acquisition (coarse) system and theAcquisition STV will show a 6’×4.4’ telescope field of view. When the carriage is at anyone position, the red LED above that button will glow. If the FP Module is powered on butnone of these LEDs is lit, the carriage may be stuck between its three normal stops. In thiscase, a manual switch on the control panel can be used to drive the carriage until one ofthe LEDs lights up. If the carriage is run past the extreme positions toward its hard limits,limit switches will disable the motor. In this case, a limit override switch on the controlpanel must be depressed and the carriage driven manually back away from the limit. Bevery careful not to drive the carriage to its hard limits! If you do, you may destroy the motoror drive nut.

The FOBOS STVs may be controlled by either the control boxes attached to the Focal PlaneModule or by the STV Remote software on the FOBOS PC. Similarly, the autoguiderSTV may be operated by the control box attached to the telescope tailpiece or by the STVRemote software installed on the Autoguider PC. Other autoguider controls include a finefocus adjustment and East/West slew controlled by hand paddles in the control room. Seethe autoguider documentation for instructions about running that system.

The 40” telescope is controlled by the DFM Telescope Control System (TCS) and by handpaddles in the dome and control rooms. The SITe GenII CCD is controlled by the Sunworkstation crux. See the manuals pertaining to those systems for more information.

4.3. Software Initialization

In an xgterm on the crux workstation, change to the $HOME/iraf/ directory and start IRAFwith the cl command. Within IRAF, change to the /data/bench/ directory and create anew directory named for today’s date. Start the ds9 software for image display. Note thatbecause crux is set up for 24-bit color, ximtool and SAOimage will not work.

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Refer to “The GenII CCD Camera System (Spectroscopy)” manual for detailed instructionsabout running the CCD control software, Voodoo. For spectrograph work, Amplifier C is pre-ferred with Gain 1.0 and Slow Integration speed (setup file /crux/bench/fobos/C1S.setup).For faint targets, Gain 2.0 may be useful (setup file /crux/bench/fobos/C2S.setup). Setthe CCD for subarray readout with dimensions 2048×200 centered at [1024, 1024]. Set theBias Position at 2080 and the Bias Width at 20. In the FITS setup menu, load the file/crux/bench/fobos/FOBOS-fits.par and check the TCS Link box. These steps will ensurethat your image headers have the keywords required for spectral reductions. Make sure theOpen Shutter, Beep, and Save to Disk boxes are checked in the main Voodoo window. Setthe output directory to /data/bench/date today/ and initialize the file name to somethinglike ccd1001.fits. Note that IRAF wants the image filename extensions to be “fits” andnot “fit”.

The STV cameras used in the spectrograph and with the autoguider may all be controlledusing the STV Remote software. Run the software on the autoguider PC and connect to theguider STV through port COM1. On the FOBOS PC, run two instances of the software.Connect to the Acquisition STV through COM1 and the Guide Fiber STV through COM2.Refer to the 40” manual for further instructions about running the autoguider. For thespectrograph STVs, it is not important to set the correct Date/Time, telescope focal length,etc.

You may begin imaging with the STV cameras immediately after establishing successfullinks. Click Image and then click Parameter repeatedly to see the adjustable parameters.Set each parameter by clicking the Value button. Choose the “Normal” zoom mode andthe ×2 gain setting. Finally, click Image again to start the continuous video stream to themonitor.

4.4. Calibration Lamp Exposures

You will want to take a set of calibration images during or before each night of observing.These should ideally be done after the spectrograph room has been prepared for observingand the air has settled (i.e. when the spectrograph room is in a state most similar tonighttime observing).

A set of milky flats should probably be taken shortly after the room is prepared in theevening. An opal glass filer must be placed in Filter Slot 2 (Figure 6) and the top of theScience Fiber Mount replaced. Move the mirror carriage to the Calib position and turn onthe QTH lamp. Take a series of exposures with a few thousand counts each. Remove the opalglass filter using the threaded brass tool next to the Science Fiber Mount and replace thetop. Allow some time for the room to settle before taking additional calibration or targetedspectra.

Ideally, the instrument should be so stable that a single QTH lamp spectrum and a singlewavelength calibration lamp exposure taken at the beginning of the night would suffice tocalibrate the entire night’s data. However, until instrument stability can be established, itis advised the QTH and arc lamp exposures be taken several times during the night. To doso, make sure the mirror carriage is in the Calib position. To take a QTH exposure, turn

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Figure 10. Full view of a 1 second QTH lamp exposure in a 2048×200 pixelsubarray centered at [1024, 1000].

on the QTH lamp and set the exposure time to something like 1 second. The wavelengthcalibration spectra are slightly trickier. In the primary instrument setup, the Neon lamp isconsiderably brighter than both the Argon and Xenon lamps. Set the exposure time to 60seconds or more. Turn on all three arc lamps. Make sure the intercom to the spectrographroom is on and the volume is turned up. Start the exposure and listen for the shutter toopen. As soon as the shutter opens, turn off the Neon lamp. Leave the other two on for theduration of the exposure.

Figure 11. Extracted raw Neon/Argon/Xenon spectrum taken with the primarysetup.

4.5. Telescope Coordinate Initialization

Following the normal start-up procedure for the 40” telescope, align the telescope on aknown, bright star using the finder scope. Move the fold mirror carriage to the Acquire

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position and begin imaging with the Acquisition STV. Select input 1 for the FOBOS STVmonitor. The bright star should be in view. Move the telescope using the hand paddle untilthe star is centered in the STV field of view. Now enter the star’s coordinates in the TCS’stelescope position initialization function.

Important: For the first few times the telescope is slewed to a new position, every time alarge (> 30◦) slew is performed, and especially when large slews toward or away from theNorthwest are performed, walk up to the dome and make sure the fiber train does not getcaught on the telescope, tailpiece, or any other foreign object.

4.6. Focal Plane Module Focus

The Focal Plane Module must be focused. This can be accomplished by moving thetelescope’s tailpiece focus until the bright star used for coordinate initialization is in focus.The distance from the fold mirror in the carriage to the focal plane ferrules is the same asthe distance from the mirror to the object plane of the coarse acquisition system. Therefore,focusing the image on the STV camera has the effect of bringing the ferrules into thetelescope’s focal plane. Note that there are aberrations in the image produced by the verysimple optical system used for coarse acquisition. Stars will appear point-like in some areasof the image, but may have a ringlike appearance with a bright, off-center core in other areas.When focusing the instrument, attention should be paid only to the bright core of the star,or better — the star should be positioned in the less aberrated area of the camera towardthe lower third of the monitor. On 13 Oct 2003, with an exterior temperature of ∼ 60◦F,the spectrograph focus was at ∼ 3350.

The star can be focused by eye, but perhaps a more accurate method is to use the “OpticalQuality” mode built in to the STV controller. Move the telescope to position the star onthe screen in an area where the optical aberrations appear minimal, but not too close tothe edge. Press the Monitor button. Press the Parameter button until you see “OPTICALQLTY”. Push the Value button. The STV should detect the star and begin monitoring itsprofile. Adjust the telescope’s focus while noting the change in the FWHM reported by theSTV. Set the focus so that the FWHM is minimized. Note that the actual number reportedis meaningless unless you enter the telescope parameters in the STV’s Setup menu (notrequired, but may be interesting).

4.7. Coarse Acquisition

Once the telescope position has been initialized, coarse target acquisition may commence.Slew the telescope to the target’s coordinates. Make sure the STV monitor switch is set toinput 1. The target should be in view. If it is relatively faint, you may need to bump up theSTV exposure times to see it.

Two science fibers are available for targeted acquisition. These are fibers 1 and 4 in Figure 12.For each of these ferrules, the science fiber is intact and the guide fibers are properlyaligned around them. Fibers 2, 3, and 5 have functional science fibers, but the guide fiberarrangements are flawed, so the prescribed fine alignment procedure will not work. However,

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North

South

East West

2 3

54

16 7

Figure 12. Top view of the Focal Plane Ferrule array.

these can be used to collect sky spectra for background removal during processing. Fibers6 and 7 are completely nonfunctional. The positions of Fibers 1 and 4 have been markedon the TV monitor with a grease pencil, with Fiber 1 being nearest the center. Using thehand paddle, move the telescope to position the target over the desired focal plane ferruleposition. Fiber 1 appears to have the best throughput, so it is preferred.

4.8. Fine Acquisition

When the star has been approximately aligned with the focal plane ferrule, move the foldmirror carriage to the Observe position. Switch the STV monitor to input 2. You should seelight coming through some/all of the guide fibers corresponding to the science fiber chosen(See Figure 13). If the target is faint, the integration time on this STV may need to beincreased in order to see the signal.

Using the hand paddle, move the telescope slowly until the light coming through all of theguide fibers equalizes. This indicates that the source is centered, and therefore over thescience fiber. This procedure will only work for point-like sources; extended objects can onlybe coarsely aligned. When the target’s fine alignment has been established, the autoguidermay be engaged if necessary.

4.9. Guiding

For shorter exposures (< 3 minutes or so), it’s probably most efficient to guide by eye. Ifthe telescope doesn’t track perfectly, you will notice the relative guide fiber light intensities

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1A 1B

1C1F

1E 1D

4A 4B

4C

4D4E

4F

Figure 13. View through the Guide Fiber STV. For this picture, the Xenon lampturned was turned on and the fold mirror carriage was in the “Calib” position. Thehexagonal array in the upper left corresponds to the guide fibers around ScienceFiber 1 (See Figure 12) while the array in the lower right correspond to ScienceFiber 4.

change. Manually move the telescope using the hand paddle in the control room to correctthe alignment.

An auxiliary autoguider is available for use during long exposures. The autoguider is anSTV attached to a piggy-backed 8” Meade telescope on the side of the 40” tube. See the40” manual for instructions on operating that system. Note that the autoguider must berecailbrated every time the telescope is moved significantly in declination. Even while usingthe autoguider, you should periodically check the guide fiber output to make sure the guidingis working well. If the alignment appears to worsen, turn off the guiding, correct the telescopealignment, and then re-engage the guider.

4.10. Throughput and Exposure times

The throughput of the FOBOS + telescope system was estimated by observing thespectrophotometric flux standard star Feige 110 under photometric conditions on UT 2003November 29. The efficiency curve (Fig. 14) is not constant with wavelength. In particular,the blue response is fairly low, and the red response drops quickly past the peak. Practically,the current setup does not actually provide 2048 pixel spectra; the throughput is low enoughat the edges of the spectra so as to render those regions useless. The instrument setup andgrating rotation should be set to optimize for the specific wavelength range of interest.

At the time that these efficiency data were collected, the telescope’s mirrors had notbeen aluminized for more than four years. Due to persistent problems with humidity andcondensation at the site combined with the advanced age of the mirror coatings, we expectthat the telescope’s efficiency has adversely affected the total system efficiency as plottedin Figure 14. Thus, the system performance will likely improve following the next mirrorrealuminization. With that caveat, estimates of peak signal to noise ratio (S/N) per pixelas a function of exposure time and target V magnitude are presented in Figure 15.

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Figure 14. Throughput vs. wavelength for the telescope + FOBOS system in theGGSS setup on 2003 November 29. The efficiency of FOBOS alone should be higherbecause we expect considerable contribution to the reduced efficiency (especiallyat shorter wavelengths) by the telescope mirrors that had not been aluminized forseveral years at the time these data were collected.

5. Shutting Down

5.1. Disabling the Vibration Isolator

On the ground floor of the observatory, turn the air compressor’s OFF/AUTO switch to the OFFposition. Turn the regulator counterclockwise to set the outlet pressure to zero. Detach theisolator’s air tube from the compressor’s air hose in the spectrograph room. To do this, pressthe the end of the red, plastic connector in while you detach the hoses from one another.Open the regulator on the compressor to depressurize the air tank. Close the regulatorwhen the pressure reaches about 20 psi. Open the drain valve under the air tank to drainaccumulated water. When the water has drained, close the drain valve.

5.2. Spectrograph Room

Carefully replace the cover on the grating and then the cap on the SLR lens. Fill the dewarusing the same procedure outlined in section 3.1.. Open the A/C door and turn the A/Cto Medium Cool. Turn on the air cleaner. Turn on the dehumidifier to the halfway point.When the dewar is full, turn off the lights and pull both doors firmly closed behind you.

5.3. Dome Room

Replace the telescope cover and send the telescope to zenith (turn off telescope tracking onthe electronics rack in the control room first). Turn on the A/C power switch. Set the heatlamp control to “humidistat” and set the humidistat to ∼50%. Power off the spectrograph

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Figure 15. Lower limit to the predicted peak signal to noise ratio per pixel vs.exposure time for different apparent magnitudes.

electronics control box, two STVs, and the autoguider STV. Close the in-tailpiece shutter.Close the exterior doors and dome slit. Turn off the lights and close the door when youleave.

5.4. Control Room

Back up your data. If you are at the end of a run, delete your files from the hard drive.After backing up your data, log off of crux. Shut down the autoguider and FOBOS PCs.Power off the TCS PC. Turn off the TV monitors. Send the Focal Plane Module fold mirrorcarriage to the Calib position. Power down the telescope and tailpiece in the standard way.Leave the FMOEMCS PC and software running. Fill out the observing log. Turn the lightsoff and close the door when you leave.

6. Troubleshooting

Problems? Here are a few suggestions to remedy problems that have occurred so far...

• Mirror Carriage gets stuck in the Calib or Acquire position:The fold mirror carriage may occasionally get stuck in either the Calib or Acquire

positions. There is a pin on the carriage that triggers various switches to shut offthe motor and stop the carriage at a given position. However, the motor occasionallydrives the carriage a bit too far, and then the limit switches are engaged, which preventthe motor from running completely. This is to avoid driving the carriage into its hardlimits and destroying the motor. To correct the problem, go to the electronics controlbox on the focal plane module and change the control to Local. Hold down the Limit

Override button and manually drive the carriage away from the limit and into the

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Observe position. Be very careful not to drive the carriage into its hard limits! If thecarriage is near the limit on the Calib side, it must be moved toward the West. If itsnear the limit on the Acquire side, it must be moved toward the East. Don’t forgetto switch control back to Remote when you’re finished. If the problem persists, notifyobservatory staff who may be able to modify the limit switch angles.

• Mirror Carriage gets stuck between designated stop positions:This appears to happen infrequently. The cause is unknown, but is suspected to arisefrom RF interference from other electronics in the dome. If the carriage gets stuckbetween stop positions, none of the LEDs on the control pad or electronics box will beilluminated. In this case, go to the dome room, switch control on the electronics boxto Local, and manually move the carrioage to the West or East until it reaches oneof the stop positions and an LED turns on. Then return control to Remote. If thisproblem persists, notify Jim Barr.

• STV shows no image:Chances are that either (1) the telescope’s pointing is off, (2) you need to increase theintegration time, (3) you have forgotten to switch the monitor to display the correctcamera output, or (4) the mirror carriage is not in the correct position. The first is byfar the most likely. The pointing model is imperfect, and we suspect that the toothlessfriction drive system may slip intermittently. If the pointing is off, go to a nearby brightstar and re-initialize the TCS coordinates. If none of the above seem to be the causeof the problem, make sure that the sky has not clouded over and that the telescope ispointed out the dome slit. Finally, check to make sure that the in-tailpiece shutter isopen.

7. Data Reduction

An IRAF package called FOBOS has been written to assist with data reductions. Thisis installed on crux at FMO and also locally in the Astronomy Department. The availableroutines include:

• foboscfg — Assists with designing FOBOS configurations for user-specified wave-length ranges.

• foboshead — Updates FITS headers with spectrograph configuration information,object names, and IRAF-friendly keywords.

• foboslogs — Generates nice postscript observing logs from FITS header information,and optionally adds comments using a user-created input file. Also can generate textobserving logs.

• fobosmlk — Generates a combined, smoothed flat field from a set of milky flatobservations.

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• fobosinc — Generates a fiber-to-fiber inconsistency file from QTH or daytime skyobservations, used to remove the effects of fiber throughput variations.

• fobosext — Extracts and identifies wavelength calibration spectra. Extracts, sky-subtracts, and wavelength calibrates target spectra.

• prep4bandit — Performs some preprocessing necessary for running the BANDITradial velocity cross-correlation software. Also generates several text files required asinputs for BANDIT.

To make full use of foboshead and foboslogs, you’ll want to keep a text comments filewhile observing. This file should have the following format: the image prefix begins eachline, followed by a colon as a field separator, then the object name, followed by a colon andany comments for the file on the same line. When running foboslogs, this file will beinterpreted by LATEX, so any special LATEX characters must be “escaped” by a backslash (\).A few lines from an example file follow:

ccd1035 : HD4388 : RVstd K3III V=7.34 v\_r=-28.3 km/sccd1036 : HD4388 :ccd1037 : HD4388 :ccd1038 : QTH :ccd1039 : NeArXe : Neon off after < 1 second

Refer to the FOBOS package help files for more detailed information. Peter Frinchaboy hasalso written a helpful “Cookbook” for FOBOS data reductions. In brief, a typical reductionfor a run might look like this:

1. Run foboshead on all FITS files.

2. Run foboslogs on all FITS files.

3. Run ccdproc on the bias frames to trim and overscan-correct. Generate a combinedbias frame with zerocombine.

4. Run ccdproc on the milky flat frames to trim, ovserscan-correct, and bias-subtract.

5. Run fobosmlk on the milky flats to create a combined flat field.

6. Run ccdproc on the QTH and/or daytime sky frames, comparison lamp frames, andobject frames to trim, overscan-correct, bias-subtract, and flatfield using the combinedmilky flat.

7. Median combine multiple exposures for each object using imcombine.

8. Extract the QTH and/or Solar spectra using apall.

9. Run fobosinc on the extracted QTH or daytime sky spectra to generate a fiberinconsistency file.

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10. Run fobosext on the object images to extract, sky-subtract, and wavelength-calibratethem.

11. Run prep4bandit only if you are going to use the MATLAB BANDIT software todetermine radial velocities.

8. Neon/Argon/Xenon Spectral Line Identification Charts

Figure 16 shows a comparison lamp spectrum taken with the primary setup in the mannerdescribed in Section 4.4.. A subset of the identifiable lines is labeled. Most of the Neon linesare considerably stronger than the bulk of the Argon and Xenon lines. However, all will beuseful for wavelength calibration provided that the strong lines do not saturate and the weaklines have good singal-to-noise.

Note that there are no line identification lists that come with the default IRAF NOAOinstallation that are appropriate for this instrument. The commonly used idhenear.dat

line list will not work well because it contains no Xenon lines, but does contain Heliumlines. A special line list, called nearxe ggss.dat has been prepared for the primaryFOBOS setup. This was created by using Argon and Neon lines taken from the IRAFhenearhres.dat line list and Xenon lines taken from the National Institute of Standardsand Technology website. Each of these lists was then used to identify lines in spectra ofindividual calibration lamps, and those lines that did not appear in the spectra were deleted.nearxe ggss.dat is what remained. Some lines in this list seem to work better than others.In particular, you may choose to delete lines that are blends or closely spaced. This line listhas been installed in the IRAF linelist libraries on crux at Fan Mountain, and locally in theAstronomy Department. To use the list with one of the IRAF identify procedures, enterlinelists$nearxe ggss.dat for the coordli parameter.

Neon is very good for the red part of the primary setup. Argon has fairly good coveragethroughout. Xenon is mainly useful in the bluer region.

Figure 17 shows a blue Argon + Xenon comparison lamp spectrum (60s exposure at lowgain) taken with the “blue grating” (1200@157 in Table 1). The line identifications, listedin the file linelists$arxeb.dat, may be useful for wavelength calibration of blue spectra.

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Figure 16. Line identifications for Neon-Argon-Xenon spectrum taken with theprimary setup (<1 second Neon + 60 seconds Argon and Xenon exposure). Notethe different intensity scales for the four panels.

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Figure 17. Line identifications (file arxeb.dat) for Argon-Xenon spectrum takenwith the blue grating (60s exposure).

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Chapter 13

The Santa Barbara InstrumentsST-8/ST-1001E CCD Cameras

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148

Santa Barbara Instruments ST-8/ST-1001E CCDCamera

(Rev. August 06, 2007)

General Information

You will be using the ST-8 camera either as an imaging camera, or as the detector for theOptomechanics 10C Spectrograph. In both cases, set up and operation of the CCD cameraare identical.

ST–8 Specifications:

Camera: Santa Barbara Instruments Group ST–8 PC operated CCD

Chip Type: Eastman Kodak KAF–1600; 2 phase, front illuminated chip

Format: 1530 × 1020 pixels 9 µm square

Spectral Range: Sensitive from 4000 – 11000 A

Read Noise: 15 electrons/pixel RMS

Cooling: On–board thermoelectric cooler

You will be using the ST–1001E as an imaging camera.

ST–1001E Specifications:

Camera: Santa Barbara Instruments Group ST–1001E PC operated CCD

Chip Type: Eastman Kodak KAF–1001E; 2 phase, front illuminated chip

Format: 1024 × 1024 pixels 24 µm square

Spectral Range: Sensitive from 4000 – 11000 A

Read Noise: 17 electrons/pixel RMS

Cooling: On–board thermoelectric cooler

This manual is designed to take you through the setup and operation of the CCD camerasstep-by-step so that you can perform your laboratory without having to rely heavily on aTeaching Assistant. The CCD is delicate, however, so if you are uncertain abouthow to do something please ask the T.A. for help before trying to do it yourself.

Throughout this manual, it is assumed that you already have a general understanding of theuse of CCD cameras. Appended to the end of this manual is a list of references to literatureon the design and use of CCDs if you need additional information not provided here.

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1. CCD Set Up

When you arrive at McCormick Observatory, the CCD (or spectrograph) mounting willalready be connected to the tail end of the 26” refractor. If it is not, only the T.A. isauthorized to change the tailpiece. Do not attempt to do this on your own.

With the tailpiece mounted on the telescope, and the CCD mounted to the tailpiece, set upis actually quite simple. The CCD needs to be connected to the control computer (an IBMcompatible PC), which requires the following steps:

1. Carefully roll PC cart from observer’s room to dome.

2. Plug powerstrip on PC cart into long orange extension cord.

3. Plug extension cord into outlet on East side of 26” pier.

4. Connect the male end of the ribbon cable into the parallel port on the PC. Connectthe female end of the ribbon cable to the parallel port on the CCD head.

5. Connect the 5–pin power cable from the CCD power supply to the CCD head. Plug thepower supply into the power strip on the PC cart. If everything is connected properlyand the unit now has power, the red LED on the rear of the CCD head will glow andthe fan will begin spinning.

6. Plug the PC and the PC monitor into the power strip on the PC cart. Start the PCby pressing the power button.

A PC is required to control the CCD’s various functions. There are two different softwarepackages installed on the PC which can control the CCD, CCDOPS and SkyPro. Bothprograms are essentially the same, the main difference being CCDOPS is run from DOS andSkyPro is run from Windows. The following sections of the manual are written assumingthat you will be using CCDOPS to control the CCD. However, SkyPro is very similar toCCDOPS, and if you prefer to use the Windows environment, you can use SkyPro.

To start CCDOPS do the following:

1. In the FILE menu select the “Exit Windows” option.

2. from the DOS prompt, type: cd CCDOPS.

3. from the DOS prompt, type: CCDOPS.

You should now see the CCDOPS software displayed on the monitor. The next section willdescribe how to control the camera with this software.

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2. CCD Operation with CCDOPS

This section of the manual covers the initialization, use, and shutdown of the CCD camerawith the CCDOPS software. If you are using the SkyPro package, the steps are similar,however, location of the commands may not be in the same menus as in CCDOPS.

CCDOPS is DOS-based software, so to maneuver through the menus you will use the arrowkeys. To select a menu item, press return when you have highlighted it. You can also usethe mouse to select menu items as you would in Windows.

CCD Initialization Prior to observing, there are several steps you should take to initializethe CCD Camera. First, you need to establish communication from the CCD head to thecomputer. To do this, simply select Establish COM link in the Camera menu. Whenthe program is started, it includes a status area on the bottom of the screen. In the camerasection of the status area it should say “Link:Not Found” when you start CCDOPS. Afterselecting Establish COM link, however, this should change to indicate that a link has beenestablished through port LPT1 to the ST-8. Once this link has been established, you canbegin using the CCD Camera.

Next, you should choose Setup from the Camera menu to set the CCD operatingtemperature, resolution, and dark frame use. To minimize dark current, you want theCCD temperature to be as low as possible. The CCD has an on–board thermoelectric coolerwhich can quickly cool the chip to low temperature. After choosing Setup in the Cameramenu, type in a setpoint where indicated. This value should be between 0◦ and -10◦ Celsius.Once you’ve entered the setpoint, switch the temperature regulation to active. The currenttemperature is displayed at the bottom of the CCDOPS screen. You can begin exposing theCCD when the temperature nears your setpoint (should be within a few minutes).

In the same Setup box, you can also choose the resolution of the camera. There are threeresolution levels, High, Medium, or Low. In high resolution mode, the chip reads out allpixels. In medium, the chip reads out bins of 2x2 pixels, and in low, the chip reads out binsof 3x3 pixels. High resolution mode is best, since you keep the most information when youread all pixels. The drawback to high resolution is that the chip read time is significantlylonger than in medium or low resolution mode. Therefore, use high resolution on programobjects, and use medium or low on focus frames, first test frames of program objects, andother throwaway exposures.

Finally, you can select whether or not you would like to take dark frames. Since this CCDis only thermoelectrically cooled to just below 0◦ Celsius, it has a significant amount of darkcurrent. Subtracting a dark frame and from your real exposure will remove fixed patternnoise from the variable dark current and bias level of the chip. CCDOPS can be set toautomatically take and subtract a dark frame from your real frame before displaying. To dothis, set dark frame to Also in the Setup window. If you will be taking multiple exposuresof the same duration and at the same temperature then you can also set Reuse Darks toYes. Note that a dark frame must be the same length as your program frame. Therefore, a15 min. exposure with a dark frame will take more than 30 minutes including readout time.The reuse dark option will significantly reduce observing time for multiple long exposures.

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Note that the CCD Camera Setup can be changed at any time during the night. You canswitch resolution, dark frame use, and temperature (although there is really no need tochange the temperature) whenever you wish.

CCD Operation Using the ST-8 CCD with the CCDOPS software is quite easy. While thesoftware has many sophisticated options, you can obtain high quality exposures very simply.There is no cookbook list of numbered steps you can follow, since how you use the camerawill depend very much on the observing program you are performing. However, there areseveral steps common to all programs which will be outlined below.

The most important thing to do before beginning your observations is to focus the telescopeas best you can. To do this, select the Focus command in the Camera menu. The Focuscommand tells the CCD to take a series of frames continuously, allowing you to adjust thefocus of the telescope in between each one. Of course, to focus the telescope, you need tohave an object to focus on, so before beginning to expose the chip, point the 26” at a fairlybright star (say 9th to 12th magnitude). In the Focus window, set the CCD to “Planet”mode. Then set the exposure delay to give you enough time to adjust the telescope focusbetween exposures (for the 26”, you will probably need at least 20-30 seconds). Finally, setthe exposure time for each frame long enough to integrate over changes in seeing, ten secondsor so is enough for a bright star. When you hit enter, the CCD Camera will begin a sequenceof exposures. Planet mode tells the camera to first take a full frame exposure. Then, afterreading this exposure out and displaying it to the screen, you will see a white box appearin your image which is smaller than the chip. You can place this white box anywhere in theimage using the arrow keys. After putting the box around the star you are using to focus,hit the return key twice. This will instruct the chip to only read out the portion of the chipincluded in the box. Chip readout times will therefore be reduced and you can focus thetelescope quickly. Once you have used the “locate” box to select your focus object, crankthe focus of the 26” 1–2 cranks between focus exposures. If for some reason you lose thestar from the “locate” box, you can restart Planet mode without exiting your current Focusrun. To do this, simply select Planet from the menu which appears in the upper left handcorner when a focus image is displayed. This will make your next frame full size again soyou can recenter your focus star.

There is a straightforward method for determining the focus of the telescope quite accurately.Begin your Focus exposure set with the telescope way out of focus in one direction. As theframes progress, slowly move the focus in or out so the stellar image begins to narrow onthe chip. To find the focus, continue doing this until you’ve gone past the focal point, andthe stellar image has begun to widen again. Once you’re sure you are past the focal point,simply go back in the other direction until you have the image as narrow as possible. Tofurther improve the accuracy, you can use the peak pixel value of the image. The numberwhich is displayed to the left of the image window gives you the value of the pixel in thedisplayed frame which has registered the most counts. As you achieve better and betterfocus, the light from a star is concentrated into a smaller area. Therefore, the value of thecentral pixel will increase as you achieve better focus. So, while you are focusing the stellarimage and minimizing its spatial extent, look for the maximum pixel value. When the imageis at its narrowest, and the pixel value is at its highest, you have achieved focus.

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After achieving focus, the use of the CCD Camera will depend on your particular observingprogram. The rest of this section will describe how to take a standard CCD exposure,which is common to all programs. To take an exposure, select the Grab command from theCamera menu. The Grab command is very similar to the Focus command, except it takesonly 1 exposure instead of a series. Simply select your integration time, and press Returnand the exposure will begin. Remember, the resolution (high, medium or low) and use ofdark frames for this exposure is set in the Setup option of the Camera menu. You can changethose options between each exposure to fit your observing needs.

In some cases, you may wish to use SBIG’s “Track and Accumulate” software as analternative to simply using the Grab command. To use this option, select Track andAccumulate under the Track menu in CCDOPS. The Track and Accumulate option allowsyou to take several shorter exposures of your program object rather than one long exposure.The software will then co-register and co-add the multiple short exposures, leaving you witha single, stacked image. Using this software option will require you to set the followingparameters:

Snapshot Time: Integration time for each exposure (60 – 120 sec is probably best).

Number of Snapshots: Number of snapshots to take and then co–add.

Dark Interval: Set this to “Series” and then the same dark image will be used for all ofthe individual frames.

Track Mode: Set this to “Align” to tell the software to co–register the images.

The other parameters for Track and Accumulate can be left with their default values.

After you begin the Track and Accumulate process, the first exposure will begin. Like theFocus command in “Planet” mode, your image will be displayed with the “locate” boxdisplayed. You now need to move the locate box until it encloses a star which can be usedfor guiding. After subsequent exposures, the software will use the pixel position offset foryour chosen guide star to perform the co–registration. For this reason, you should select afairly bright star away from the edges of the chip as your guide star.

CCD Shutdown When you are finished with your observing program, you will need toshutdown the CCD and computer system. First, select Shutdown from the Camera menu.This terminates the communications link from the CCD to the computer. Next, select Exitfrom the File menu. This will return you to the DOS prompt. You can now turn the PC offby pressing the Power button. Now simply perform the setup in reverse. Remove the powercable from the CCD head and roll it up. Remove the ribbon cable from the CCD head androll it up. Unplug all plugs and store them on the cart as you found them when you arrived.Roll the cart slowly into the observer’s room for storage.

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CCDOPS miscellanea As mentioned above, CCDOPS contains many more options thanthose described in this manual. You will probably not need to use any of them other thanthose described above, however. If you are performing a lab which does require some otheroption, either the TA or the lab manual will describe how to use it. This last section will goover a few final details about using CCDOPS.

At any time, hitting the Esc key on the keyboard exits what you are doing. So when you arefinished with your focus run, or if you want to abort a long exposure because of a problemwith the telescope, etc., simply hit Esc. Also, after your exposure taken with Grab hasfinished and has been displayed to the screen, Esc gets you back to the main CCDOPSscreen. The current image is kept in the image buffer until it is saved to disk or anotherexposure is taken. So after your image has been displayed and you have hit Esc, you cancontinue to redisplay it until you save the image or replace it with a new one. To redisplayit, select Image from the Display menu. This option also allows you to change the displayparameters so that you can enhance faint detail or only display the brightest portions of theimage. To change the display parameters, simply type in a new background and range whereindicated in the Image window.

In addition to changing the display parameters with Image, you can also get some usefulinformation about your image. Set the “Display Mode” in the Image window to “Analysis”after you have selected Image from the Display menu. You will notice a menu of optionsnow available in the upper left hand corner of the display. If you select “X-hairs” (or simplytype X), a set of crosshairs will appear on the display. The box in the upper left hand cornerwill now display the pixel position and value for the current pixel.

Finally, you will want to save your images to disk so that you can retrieve them later fordata reduction and analysis. If you will be porting the images to the department’s UNIXWorkstations for analysis in IRAF or IDL, you will want to save your images in the FITS(Flexible Image Transport System) format. To do this, simply select Save in the File menu.Type in a unique name for your image and then set the “Type” to FITS. A second windowwill appear, titled “Save FITS Image”. In this window, set “Bits per pixel” to 16, andtype in any comments you would like in the fields indicated (Telescope, Observer, Object,Comments). When you hit Return, the current image will be saved to disk.

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Chapter 14

The OptoMechanics Model 10CSpectrograph

155

156

OptoMechanics Model 10C Spectrograph(Rev. August 09, 2011)

1. General Information

Certain laboratory exercises will require you to use the Spectrograph and CCD togetherinstead of simply doing straight CCD imaging. The CCD setup and operation are identicalto that described in the first part of this manual. This section is designed to take you throughthe setup and operation of the spectrograph so that you can perform your laboratory withouthaving to rely heavily on help from a Teaching Assistant. Like the CCD, the spectrograph isa delicate instrument and should be treated with care. The optical elements, in particular,are very expensive (as is the CCD). As with all delicate equipment, NEVER force any movingpart beyond reasonable and expected resistance. Never move the telescope by pushing on thespectrograph or CCD, and never lean or support yourself by holding onto this equipment.Never, NEVER, touch any optical element. Oils from your skin will permanently embed intoglass surfaces and optical coatings. It is preferable to leave small amounts of dust on opticalsurfaces rather than risk scratching or marring the surfaces with attempts at cleaning. Ifyou are uncertain about how to operate any aspect of the spectrograph, please consult theT.A. for help. THINK BEFORE DOING.

Just as in the CCD section, this section will assume you have a general understandingof spectroscopy. You will find information on spectroscopy in the references listed in anappendix at the end of this manual if you need more information not provided here.

2. Use of the Spectrograph

2.1. Instrument Design

Figure 1 gives a view of the spectrograph and mounting at the tail of the 26” Clark refractor.An external view of the grating assembly including the dial can be seen in Figure 2. Figure3 shows a layout of the internal optical design of the instrument. A sample spectral imageof a star and comparison sources is in Figure 4.

The major elements of the instrument are:

Instrument Rotation Ring: This allows rotation of the slit angle on the sky. At present,there are detents every 15 degrees of rotation, but random angles are also possible. Donot rotate slit position angle without TA assistance. The default position angle is 90degrees.

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Focal Reducer: The first optical element of the spectrograph is a transfer lens. This lensserves to speed up the (rather slow) f/14.9 refractor telescope beam to f/10.

Slit Assembly: At present, there are two slits available with spectrograph, a 50µm widthslit which is equivalent to ∼ 1.5 arcseconds (calculated with f/10 and 26” aperture),and a 100 mm width slit which is equivalent to ∼ 3.1 arcseconds. You can tell whichslit is in the beam by the color of the round knob (see Figure 1): black is the 50µmand silver is the 100µm. The “slit” is actually a set of three slits end-to-end. Yoursky source will be imaged onto the central slit, which is 1.5 mm = 46.8 arcsecondsin length. The two side slits are fed light from the comparison source via fiber opticcables for simultaneous recording of astronomical and comparison source spectra.

Figure 1. The Spectrograph and Mounting on the 26-inch Clark Refractor.

Comparison Source: At present there are two available comparison lamps, mercury andneon/argon. In general, you will want to use both sources, although certain spectralregions are devoid of lines from one or the other. If this is the case for your particularwavelength set-up you can extend lamp life by using only the source needed for yourwork. The lamps have been intensity balanced to achieve approximately equal lineintensities; however, these lamps do have a limited lifetime which results in gradualdimming. If you should notice peculiar line intensity ratios between the mercury andneon for the same exposure time, notify the TA. In this spirit, please DO NOT LEAVE

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Figure 2. This image includes the grating knob, the counter displaying degrees oftilt angle (here, 28 degrees), as well as the lock to hold the grating at the specifiedangle.

THE LAMPS ON for more than the time required to make your comparison spectrum(typically ∼1−5 seconds). An atlas of the Hg-Ne/Ar source lines is given in AppendixA.

Guide Eyepiece: At present, acquiring objects and guiding the telescope is done manuallythrough the guiding eyepiece assembly. The image plane of the telescope (when infocus) is on the slit “jaws”; an aluminized mirror surface into which the slit holes arecut. Thus, through the guide optics you observe that part of your source which doesnot fall through the slit. Your goal in guiding the instrument is to ensure that as muchof your source flux falls through the slit as possible, and in general at the same placealong the slit.

Collimator: The collimator is a 225 mm focal length mirror which converts the convergingtelescope beam into a collimated beam.

Grating: Four gratings are available with this spectrograph with rulings of 240, 400, 600and 1200 grooves per mm (at present, we do not have the 400 line grating). All areblazed (yield maximum reflection) near 5000A. When used in first order, these gratingsyield spectral resolutions of 295, 180, 120, and 60 A/mm. Note that the ST8-CCD haspixels of size 9µm (at high resolution; when binned, the pixel size changes accordingly),a limitation which must be included in any calculation of the true resolution.

You may NOT change gratings yourself. In general the grating needed for yourexperiment will be in place before you arrive at the Observatory. If this is not thecase, please ask the TA for any changes. In order to remove the grating:

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1. Set the tile angle to 35 degrees.

2. Unscrew (but don’t remove) the 3 recessed 4-40 sockethead screws that fasten thegrating assembly to the housing.

3. Carefully withdraw assembly from housing. NOTE THAT GRATING ISUNCOVERED AND FACING CAMERA.

4. Immediately and carefully install cover on grating cell, to protect grating duringsubsequent handling and storage.

5. Turn over assembly and remove the two 8-32 sockethead screws holding the gratingcell to the assembly.

6. Install new grating cell and remove its cover just before replacing the assemblyback into housing (STORE COVER IN SAFE PLACE).

The spectral region delivered from the grating to the detector is determined by thegrating tilt, controlled by the lockable knob with counter (Figure 2). The counterdisplays degrees of tilt angle (always approach final tilt setting from lower values forreproducible results). Zero tilt angle is when the grating acts as a normal mirror. Tablesof central wavelength delivered as a function of grating tilt are given in Appendix B.Note that the knob is quite loose until locked, so that if you do not lock the knob, yourun the high risk of your spectral region shifting with time and telescope angle.

In principle, these gratings can be used in other than first order; in practice, both therefracting optics of the telescope as well as the CCD detector have limited spectralrange (centered on the yellow part of the spectrum) which limit access to other orders.For this reason, the spectrograph does not presently have capability for adding orderblocking filters. However, it is good practice when working with a spectrograph toconsider the possibility of spectral contamination by higher orders.

Camera: The camera for this spectrograph is a 135 mm focal length Nikon lens for a 35mm camera. It is focused in the usual way a camera lens is focused, by rotation of theknurled outer ring.

Detector: The standard detector for the spectrograph is the ST8 CCD, although otherdetectors (e.g., a 35-mm film camera) may also be used. Do not attempt to removethe CCD without TA assistance. With spectrographs on large telescopes, the firstoperation of an observer is to ensure that the detector is rotated so that the spectrumis aligned straight along CCD rows. However, as this is a delicate operation with the10C, only the T.A. is allowed to perform this operation, which will be accomplishedbefore you arrive. However, you should check the detector alignment by checking theplacement of the same line on the pairs of comparison source on either side of yourimage.

DURING YOUR WORK WITH THE SPECTROGRAPH, YOU ARE ALLOWED TOMANIPULATE THE FOLLOWING WITHOUT T.A. ASSISTANCE:

• Telescope

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• Telescope focus

• Guider eyepiece focus

• Camera focus

• Grating tilt

• Comparison source power

• CCD camera

YOU MUST NOT DO THE FOLLOWING OPERATIONS WITHOUT TA OR FACULTYASSISTANCE:

• Change slits

• Change gratings

• Change comparison sources

• Rotate instrument position angle

• Rotate CCD on spectrograph

2.2. Spectrograph Set Up

Generally, when you arrive at McCormick Observatory, the Spectrograph mounting willalready be mounted to the tail end of the 26” refractor, with a specific grating and slitappropriate to your experiment, and the ST-8 CCD connected to the camera optics of theSpectrograph. The equipment is generally protected with the silver cover, which you mayneed to remove. In addition to the CCD setup as described in section 1.1 of this manual,there is only 1 additional step required for preparing the spectrograph.

The spectrograph has two comparison lamps in a black housing connected to the main (blue)portion of the spectrograph. These lamps need to be plugged in to the powerstrip on the PCcart with the extension cord provided. You do not need to turn on the comparison lampsuntil they are needed, so for now simply plug in the lamps but leave them off.

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Figure 3. The Optical Design of the Spectrograph.

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2.3. Spectrograph Operation

The ST-8 CCD camera is usually used as the instrument detector for the 10C Spectrograph.Familiarize yourself thoroughly with operating this device before proceeding.

Before you start observing, you need to initialize the ST-8 using the MaxIm DL imagingsoftware . Operation of the CCD is no different when using the spectrograph than if you weredoing straight CCD imaging. However, since with spectroscopy you will often be workingcloser to the background levels of the CCD, it is important to make sure that the CCDtemperature is cold (at least -10 C) and stable throughout your observations.

Using the spectrograph is slightly more complicated than straight CCD imaging, and youshould follow the steps below. In some cases, you may need to iterate between steps.

2.4. Slit and Grating

Verify that you have the appropriate slit and grating for your experiment (see above). Checkthe position angle (PA) of the slit on the sky and see if it matches your needs. In general,PA = 90 degrees (East-West) is recommended. If the position angle needs to be rotated,contact the TA.

2.5. Camera Rotation

It makes sense, whenever possible, to align the dispersion axis of the spectral images alongthe rows of the CCD (i.e., along the long dimension). You obtain about 50% more spectralcoverage on one image if you place the dispersion along the long axis of the CCD than alongthe short. If the CCD is not oriented in this way, discuss the matter with the TA. The imagein Figure 4 was made with the dispersion in the less favorable CCD orientation.

Take a short exposure with a comparison source on, and verify – by comparing the positionof Hg-Ne/Ar lines on each side of the image – that the CCD detector is aligned with thespectrograph (to within a pixel or two on either side). If the two comparison spectra are notwell aligned (parallel), notify the T.A. Check also that the camera is tightly held onto thespectrograph; if the camera is loose, you may get unwanted rotations introduced into yourimages as the telescope moves around.

2.6. Spectral Range

Based on the goals of your experiment, you should have a clear idea of the spectral region yourequire. Based on the grating dispersion and the fact that the ST-8 has 1530 pixels of 9µmsize along the dispersion axis, you can calculate your approximate accessible spectral range.You will want to vary the central wavelength so that that available range contains yourdesired astrophysical spectral features. For example, if you are observing planetary nebulae,which have the prominent [O III] emission line doublet at λ = (4959, 5007), you will wantto have the central wavelength set to ∼5000A. Appendix B lists the appropriate angles and

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Figure 4. Example spectrum of a V = 5 M star taken with the 240 line mm−1

grating centered at about 5000A. Exposure time was 45 seconds for the star and 1second for the calibration lamps; with 2x2 binning, the maximum flux on the redend was 12,500 ADU. However, due to the effects of chromatic aberration from the26-inch lens and the focal reducer, the image of the star fans out as it goes out offocus in the blue. As a consequence of this and the transmission properties of thesystem, the spectrum quickly drops in level to 0 ADU.

wavelengths for a given grating. The spectrum in Figure 4 is with the low resolution, 240

line mm−1 grating and centered near 5000A.

Tilting the grating determines the central wavelength of the resulting spectrum. To set the

grating tilt angle, you simply unlock and then turn the knob on the side of the spectrograph

housing. It has an “odometer”–like counter next to the knob which tells you the tilt angle

in degrees. To unlock the knob, slide the black lock underneath the knob to the left. Then,

twist the knob so the meter reads the angle required. When it is set, slide the lock back to

the right. When setting the angle by twisting the knob, you will notice there is a significant

amount of backlash. Therefore, you should always approach the desired value from a lower

value of the angle. In this way, you are most likely to match your setup should you need to

return to it in the future.

Because the tilt knob turns so freely, please take care to slowly move the grating.

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2.7. Focusing the Spectrograph

There are two focus operations involved in the use of any spectrograph: (1) You must firstfocus the exit beam from the grating onto the detector, and (2) you must focus the entrancebeam from the telescope into the spectrograph onto the image plane of the slit. Astronomicalspectrographs require one additional focus operation, which is that of the guiding optics onthe image plane of the reflecting slit surface. Before taking a spectrum of your programobjects, you will need to carry out these three focus operations. Remember that yourspectrograph is most efficient when both the telescope and camera are in best focus, asthis concentrates light from your source onto the smallest number of CCD pixels (increasingsignal–to–noise). In addition, the best spectral resolution with any particular grating/slitsetup is achieved when the camera is in best focus.

First, you must focus the spectrum on the CCD using the calibration lamps. This is doneby turning the camera lens which is connected to the CCD head just as if you were focusinga normal 35 mm camera. You will also need to take short 1-3 second exposures. You canevaluate the focus by using MaxIm DL to extract vertical plots of the calibration spectra.First, turn on one of the calibration lamps to use as the spectrum for focusing (we recommendthe Ne lamp because of the numerous amount of available lines). Open the ‘Focus’ tabin the ‘CCD Control’ window and take a short exposure of the entire CCD (make sure‘Continuous’ is not checked). Place the cursor as a thin box traversing a close line doubleton the calibration source spectrum to select a subframe. Check the ‘Continuous’ option andclick ‘Start Focus’ to run the feed at 1-3 second exposures. With the ‘Line Profile’ tool,place a vertical line cut across the doublet (which should appear as a double humped curvein the plot).

Begin with the camera lens turned to one limit and slowly adjust the camera lens focus bytwisting the barrel of the lens. Look for the point in the graph at which the lines in thedoublet become the most distinct from one another. This should coincide with the point atwhich the peak flux in the lines is greatest. At first, you may require large turns to get thefocus “in the ballpark”; but when closing in on the best focus, small turns of the lens yieldnoticeable results. You may need to iterate back and forth to find the very best position.The best focus is achieved when spectral lines are narrowest, when the maximum count valueis the highest, and when pairs of lines appear most clearly separated.

It is important to remember that lenses suffer from chromatic aberration. Because the systemyou are using has three lenses (telescope, focal reducer and camera) it may not be possibleto have your entire spectrum in focus at the same time. Figures 4 & 5 shows what happenswhen chromatic aberration affects a spectrum. Based on your experimental goals, you willhave to decide where you want your best focus. Note that simply focusing on the center ofthe CCD chip means that the majority of the spectrum will not be in best focus. If you areinteresting in achieving the best possible focus along the entire dispersion, it is often best tofocus at about 1/4 of the way from either end.

Next focus the guide eyepiece on the slit. First put an eyepiece in the black tube projectingfrom the side of the spectrograph if there is not one already there. Depending on the natureof your source (bright versus dim, compact versus extended), you may find that you need ahigher or lower magnification eyepiece for optimal guiding.

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Turn on one of the comparison lamps using the toggle switches on the lamp housing. Twistthe eyepiece in and out of the tube until the slit (the black lines visible against the comparisonlamps) is in sharpest focus. Do not be confused by the comparison lamps; when the slit isin focus in the eyepiece, the comparison lamps will be out of focus.

Finally, you will need to focus the telescope image on the slit. To do this, first point the26” at a bright star or planet. If you are pointed correctly, you will see your object in thespectrograph eyepiece. Note that you will see the silhouettes of the comparison source fiberoptic assemblies against the (brighter) night sky. With your bright object in the center ofthe field of the spectrograph eyepiece, crank the telescope focus until the image is in focus.The most accurate way to focus your object is to go through the focus and then go backslowly until you have the image as small as possible. Because the entrance beam to theslit is fairly slow (about f/10 after the focal reducer), it may be hard to tell when you haveachieved best focus. In this case, you should take a series of CCD images with a bright starcentered on the slit. Take exposures sufficiently long to integrate over the seeing (i.e., morethan a few seconds), but short enough that your stellar spectrum is not saturated. At first,you may want to test the focus once every three or four complete cranks of the telescopefocus, until you can zero in on the approximate region of best focus. Then do another focusseries, with steps of 2 cranks in between, and so on. Depending on the seeing, the smallestfocus difference you may be able to discriminate may be 1-2 cranks. Best focus is achievedwhen the spectrum is narrowest or has the highest flux in the central pixels.

2.8. Observing with the Spectrograph

Once you have set the focus of all three components of the spectrograph system, you are readyto begin observing your program objects. First point the telescope at the object you wishto observe. Once it is aligned in the finder, it should be visible through the guide eyepieceon the spectrograph. You will then need to adjust finely the position of the object so that itis bisected by the slit. In some cases (e.g., to observe two nearby objects simultaneously, orto align along the major axis of a galaxy or nebula) you may need or desire the slit to be inanother orientation on the sky. Ask the T.A. to rotate the spectrograph position angle foryou.

If there are no other considerations, we recommend using the spectrograph in a positionangle of 90 degrees (i.e., an East-West slit). The slow telescope motion is much easier tocontrol in the declination than in the right ascension direction, so it easier to place objectson the slit if the slit is at PA = 90 degrees. To place an object on the slit in this orientation,first roughly center the object in right ascension above or below the slit. Then lower or raisethe object onto the slit with the declination slow motion.

When the object is aligned with the slit you are nearly ready to observe. Remember thatyou must make sure the object remains on the slit in the same position throughout theentire exposure to maximize efficiency. It is a good idea, therefore, to guide the exposurethroughout the integration. Your goal in guiding is to ensure that as much object flux fallsthrough the slit as possible, and in the same place along the slit. Thus, you will be guidingon the edges of objects – those parts that do not fall through the slit. Here, again, we have

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found using PA=90 degrees to be an advantage. The 26-inch seems to track fairly well inright ascension over the course of several minutes, and is even more steady in declination.Thus, it makes sense to keep the narrow dimension of the slit in the north-south direction,where there will be the smallest telescope movement (though refraction will come into playfor long exposures at high zenith angle). At PA=90 degrees, any mistracking of the telescopein hour angle will be along the slit and, while not optimally concentrating flux in the fewestnumber of pixels, at least no flux is lost in this situation.

Take exposures using your favorite software package such as MaxIm DL. You will need tocompare the spectrum of your object to the Hg-Ne/Ar comparison lamps for wavelengthcalibration purposes. Therefore you need to turn on the comparison lamps briefly duringyour exposure. Be sure not to leave them on too long, or they will saturate and you will notbe able to accurately wavelength calibrate your spectrum. You may also risk ruining yourobject spectrum from charge leakage by supersaturated pixels. You will also shorten thelifetime of the comparison lamps. We have found that with 2x2 on-chip binning of the CCD,comparison lamp exposures of about 1 second are fine with the lowest resolution grating(240 lines mm−1).

Keep in mind that the chip saturates at 65,535 ADU, and both your object spectrum andcalibration lines must be below this to be useful. As a guide, with 2x2 on-chip binning andthe 240 lines mm−1 grating, magnitude 4-5 stars will saturate the chip in about a minute.

During your observations take care that the instrument will not run into anything (pier,ladder, fellow students) and be mindful of all cables.

When you are finished observing, follow the usual CCD shutdown procedures. The onlyadditional step necessary for shutting down the spectrograph is unplugging the comparisonlamps, rolling up the cord, and putting the cover on the spectrograph.

3. Reduction of Spectrographic Data

3.1. Preparation

Once you have finished observing and are ready to analyze the data, you can loginto one the Department of Astronomy’s Astro 3130 Windows XP workstations (Room233). See the the Computing Handbook (http://www.astro.virginia.edu/∼hbp4c/comp-uting/handbook/Computing.pdf) for more information. You will be able to use the MaxImDL and/or MIRA software package (whichever you prefer) to reduce and analyze your CCDdata. The astro3130 account should already be set up to run these programs. Contact yourTA if this is not the case.

First it is important to make a directory for the raw images (e.g., “raw”) that were taken atthe telescope and a separate directory for all your processed images (e.g., “proc”). This willprevent you from overwriting your raw data, which should be kept as is. These subdirectoriescan be made in your group directory on the astro3130 network drive (Orion). You shouldstart by making copies of the raw images and putting them in the “proc” directory.

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3.2. MaxIM DL

In order to dark subtract an image, have your image frame open along with the correspondingdark frame of equal integration time. Open the Pixel Math command via the Process menu.Set the following options:

• Image A: Select your image frame file from the drop down list.

• Image B: Select your dark frame file from the drop down list.

• Scale Factor %: Make sure both of these are set to 100.

• Operation: Subtract.

• Add Constant: 0.

Hit OK and save the new image under a file that indicates it has been dark subtracted (ie.“Image sub.fits”).

With the Line Profile tool, take the mean over many columns by using a vertical box selectionmethod in order to increase your signal-to-noise and to overcome the differences in focus withwavelength. After choosing the Vertical Box and Mean option in the Line Profile window,draw a selection box down the length of the spectrum that has a width approximately equalto the size of the out-of-focus flared portion.

Click the Export button to output the resulting plot to a .csv file to be opened with MicrosoftExcel or some other spreadsheet program. Using the comparison lamp spectra as a guide(Appendix A), place a wavelength scale on each spectrum.

3.3. MIRA

Have two images open in MIRA, the combined dark image and the object image. Open eachimage separately (i.e., not as an Image Set). Make the object image window the ‘active’window. This is done by clicking on that image.

Under Process\Math, select ‘Image Arithmetic’. Under Image, choose the frame thatcontains the spectrum you want to analyze, choose ‘Subtract’ as the Operation, and chooseyour dark frame as your Operand Image. Click Process and then save the new object imageusing ‘Save as’; select a new name for the image so as not to overwrite the old image (ie.“Image sub.fits”).

Repeat this same process for all of your observations.

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4. Ne–Hg/Ar Comparison Sources

Wavelength source: National Institute of Standards and Technology (NIST).

For reference, H-Alpha and H-Beta occur at 6563 and 4861 Angstroms, respectively.

Figure 5. A composite of the wavelength calibration spectra. The left spectrumcorresponds to the Neon calibration lamp, while the right shows the Mercury/Argoncalibration spectrum (Argon lines are the broad, dark lines above 7000 Angstroms).The middle strip contains the combination both lamps. These spectra were takenusing the low resolution 240g/mm grating.

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5. Central Wavelength vs. Grating Tilt

240 g/mm Grating 400 g/mm Grating

Wavelength (A) Tilt (◦) Dispersion (A/mm) Tilt (◦) Dispersion (A/mm)3500 2.60 290.2 4.35 176.04000 3.00 290.9 5.00 176.64500 3.35 291.6 5.60 177.25000 3.70 292.2 6.20 177.85500 4.10 292.8 6.85 178.36000 4.45 293.5 7.45 178.86500 4.85 294.1 8.10 179.47000 5.20 294.7 8.70 179.97500 5.60 295.3 9.35 180.38000 5.95 295.9 9.95 180.88500 6.35 296.4 10.60 181.29000 6.70 297.0 11.25 181.69500 7.10 297.5 11.85 182.010000 7.45 298.1 12.50 182.4

600 g/mm Grating 1200 g/mm Grating

Wavelength (A) Tilt (◦) Dispersion (A/mm) Tilt (◦) Dispersion (A/mm)3500 6.50 118.7 13.15 60.94000 7.45 119.2 15.05 61.24500 8.40 119.7 17.00 61.45000 9.35 120.2 18.95 61.65500 10.30 120.7 20.90 61.76000 11.25 121.1 22.95 61.76500 12.20 121.5 24.95 61.77000 13.15 121.8 27.05 61.57500 14.10 122.1 29.15 61.38000 15.05 122.4 31.30 61.08500 16.00 122.7 33.50 60.69000 17.00 122.9 35.75 60.19500 17.95 123.1 38.10 59.510000 18.95 123.2 40.50 58.7

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6. References on CCD Imaging and Spectroscopy

The preceding sections of the manual all assume a general knowledge of CCD Imaging andSpectroscopy. Prior to performing a CCD or Spectrograph laboratory exercise you shouldhave received instruction on these instruments in class. If you wish to read about thesesubjects in more detail, however, the following list of references may be useful:

• Fillipenko, A. V. 1982, PASP, 94, 715

• Kitchin, C. R., 1991, Astrophysical Techniques (New York: Adam Hilger) Sections 1& 4

• Lena, P., 1988, Observational Astrophysics (Berlin: Springer) Sections 5 & 7

7. File Transfer to UNIX Workstations

After your observations have been completed, you will want to analyze your new data.You will most likely be using the UNIX based astronomical data reduction software IRAF(Image Reduction and Analysis Facility) or IDL (Interactive Data Language). Both of thesepackages will read FITS (Flexible Image Transport System) images, so it is imperative thatwhen you save your images on the PC, to save them as FITS files and not TIFF or PCcompressed/uncompressed files.

To use IRAF or IDL to analyze your images, you first need to transfer the files to theAstronomy Department’s UNIX workstation cluster. To do this requires the following steps:

1. Wheel the PC cart to the “museum area” of the observatory.

2. Connect the co–ax ethernet cable to the port on the back of the PC.

3. Boot up the computer.

4. If the computer is not already at the DOS prompt, exit Windows.

5. At the Dos prompt, type: ftp astsun.astro.virginia.edu

6. Login to either your account, or the class account (e.g. astr3130) on astsun.

7. cd to the directory on astsun where you would like the images to be stored.

8. type: lcd \ccdops to get to the CCDOPS directory on the PC.

9. type: binary to ensure your images are transfered in the proper format.

10. type: put filename replacing filename with the name of the image you have storedon the PC’s disk.

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11. repeat the item 7 until you have transferred all of your images.

12. type: bye to exit ftp.

With several classes using the PC for CCD operation, the disk will eventually fill up. Youwill therefore need to eventually delete some of your images from the PC disk after you havetransferred them to the UNIX machines. However, DO NOT delete your images from thePC until you have tested them on the UNIX machines to make sure they were transferredproperly.

8. Reduction of Spectrographic Data with IRAF

8.1. Viewing and Extracting Spectra

Once your spectral image is transferred to the Unix environment (Appendix D: File Transferto UNIX Workstations), you can begin sophisticated analysis. If you are already familiarwith the IRAF environment you know a number of ways to display and manipulate images.The following section supposes a familiarity with IRAF, and is intended primarily as asuggested approach to begin evaluating data and testing images from the spectrograph.

The spectra imaged by the spectrograph may not be perfectly aligned along columns, andthe transmission optics of the spectrograph introduce some geometric distortions. Thus amore sophisticated approach is generally needed to view a spectrum than simply plottingcolumns or rows, and better sky subtraction is possible when these geometric problemsare accounted for. The IRAF apall package is designed to do this preliminary geometriccalculation, spectral extraction, and sky subtraction. The following is a cookbook to getstarted with apall, but you are strongly urged to read the help manual for apall to branchout from the technique outlined below.

8.2. Setup

Once in the IRAF environment, you must load the spectrographic IRAF processing packages;enter the following that are needed:

cl> onedspec<cr>,on> twodspec<cr>,

and

tw> apextract<cr>.

If spectra lie along CCD rows, enter:

ap> dispaxis=1<cr>.

If along columns:

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ap> dispaxis=2<cr>.

Next, set the processing parameters for apall. Apall is a program that converts your two-dimensional image into a one-dimensional, extracted spectrum that is also sky subtracted.It does this by coadding pixels optimally across the dispersion direction (along the slit) ofyour spectrum at each pixel position along the dispersion, and then subtracting evaluationsof the adjacent sky along the dispersion.

If there are doubts that the previous user may have left the apall parameters set in disarray,enter:

ap> unlearn apall<cr>

Then, enter:

ap> epar apall <cr>

and, with the <down> or <up> arrows, examine the parameters and reset the onesmentioned below. Any that are not mentioned may be left as is. To change a parameter,move to it with the <up> or <down> arrow, type in the new value, then move on. You donot need to type a <cr> with each new entered value. The editting process is terminatedwith a control-<d>.

Parameters to set or modify:

First group:format: multispecinteractive: yesfind: yesrecenter: yesedit: yestrace: yesfittrace: yesextract: yesreview: yesextras: no

Default aperture parameters:lower: -2.5upper: 2.5

Default background parameters:b funct: chebyshevb order: 1b sample: -8:-4, 4:8b nave: 1b niter: 3

Automatic finding and ordering parameters:nfind: 1minsep: 25

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Tracing parameters:t nsum: 25t step: 25t nlost: 3t niter: 1

Extraction parameters:background: fitskybox: 1weights: variancepfit: fit2dclean: yesreadnoise: 15gain: *

*To be determined.

8.3. Usage

You must convert your FITS format frames to IRAF format. By way of example, a FITSframe called ccd117.fits would be converted as follows:

cl> rfits ccd117.fits<cr>

then answer

IRAF filename: ccd117.imh<cr>

to the “IRAF filename:” output file query. Unlike with most IRAF tasks, the extensions .fitsand .imh should be typed in full.

The use of apall described here is in interactive mode. This is recommended for getting yourfeet wet with the process. There are many layers of complexity you can add to this simplecookbook reduction with increased knowledge of apall. For example, cosmic rays in longerexposures of faint objects may occasionally require deviations from the process described.In this case, however, it is generally best to take multiple exposures (at least three) andattempt cosmic ray cleaning by stacking the images with the IRAF combine task, aftersetting the combine option to “median” and the reject option to “avsigclip”, for example.

Two processes are here described: one for bright objects where a continuum spectrum isobvious across the entire spectrum, and one for faint objects where the continuum is faintor nonexistent.

For Bright Objects:

After converting to IRAF format, start the reduction of a frame with the example nameccd117.imh as follows:

ap> apall ccd117.imh

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Answer the first three questions asked with the default response (yes), which can be enteredsimply with a <cr>.

The first graph shown in your gterm window is a section cutting across the spectrum alongthe slit. The finding algorithm will indicate what it thinks is the location of your objectspectrum. If you had centered the object in the slit, then the spectrum should be in thecenter of the image. If the automatic selection looks right, typing a <q> will accept it andmove to the next step of processing. Occasionally the selection will not be correct, as in thecase of a very bright cosmic ray contamination, or in the case of a brighter source somewhereelse in the slit, or in the case that the comparison source was selected. If you wish to alterthe selection of object spectrum, strike a <d> to “delete” the automatic selection, place thecursor on the correct feature, and then strike <n> to select a “new” choice; then hit <q>to move to the next step. Respond with <cr> acceptance of default “yes” answers until thenext graph comes up. If you wish to abort the procedure at any time, begin entering “no”responses to queries until you exit the program.

The second graph shows the location on the chip where the spectrum was traced at eachpoint along the dispersion. It corresponds to the centroid of the cross-section of the spectrumalong the slit at closely spaced intervals along the dispersion. Not infrequently, a hot pixelor cosmic ray will introduce unacceptable deviations. When this happens, the program mayautomatically delete points in the interactive fitting procedure, or you can delete the pointsby hand by placing the cursor on the point and typing <d>. Refit the spectrum by typing<f>. You may want to improve the fit to the trace by changing the order of the fittingfunction (to, say, third order), by typing:

:order 3

or by changing the fitting function to a Legendre polynomial or a spline3,

:function spline3

Always refit the spectrum with a <f> after any such alterations. You may finish the fit bytyping <q>. Apall will then ask if this fit information should be added to the database, towhich a <cr> response will give the default (yes) response. Next, you will be asked to reviewthe spectrum (yes), and to show the spectrum (yes). If all is well, a graph showing yourspectrum will appear. However, if the spectrum was too faint, the program may bomb herewith a variety of error messages, and you may have to use the other method for extractiondescribed below. The graph displayed is the raw spectrum. If the object is faint, or theexposure is long enough to accumulate cosmic rays that dominate the graph scaling, theordinate may be set so that your object spectrum is unusably compressed. You may redothe display by placing the horizontal cursor just above your spectrum and typing a “>”symbol, and then below your spectrum and typing a “<” symbol. Alternatively, you mayquit the plot with a <q> and redisplay using the splot task. When you quit, a <cr>response to the query about whether to write the plot to the disk. The program will askyou the name of the file into which to write out the extracted spectrum. It will pick a nameit likes, but this name may be too long for your liking (the IRAF default is designed toaccommodate multiple spectral extractions from one image), and you may wish to type anew name. Whatever you type will be appended with the suffix “.ms.imh”. For example,

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if your image name is “ccd117.imh”, you may type in that you want the extracted, one-dimensional spectrum to be named “ccd117”, and the raw, 1-D spectrum will ultimately beput into an IRAF format file called “ccd117.ms.imh”.

You may then examine your spectrum with the IRAF program splot, by typing

ap> splot ccd117.ms <cr>

The splot package allows a very broad variety of manipulations that the user should perusetyping

ap> help splot <cr>

For example, you may set the x and y windowing of the plot with “:/xw” and “:/yw”commands. A very useful feature is boxcar smoothing excessive noise in your spectrum bytyping <s> and entering the smoothing width in pixels (3 or 5 are good values) followed bya <cr>.

For Faint Objects:

The procedure for faint objects is almost the same as given above for bright ones, with theexception of two parameter changes. An object that has a very faint continuum can nolonger be extracted properly, since the centroid of the spectrum may no longer be traceable.In this case, you must have another exposure of a bright source in the same slit position asa reference. You need to turn off the automatic ”fittrace” routine and tell the program torefer to the other image. You can do this with the invocation of the apall routine as follows:

ap> apall ccd117 refer=ccd116 -fittrace <cr>

where in this example the reference spectrum is contained in the image ccd116.imh, which hasalready been reduced into ccd116.ms.imh beforehand. The minus sign before the “fittrace”turns off that option. Note: because of the effects of atmospheric dispersion, there may bedifferential shifts of wavelengths along the slit (see Fillipenko, 1982, PASP, 94, 715 for adescription of the effects of atmospheric dispersion on spectrophotometry and how properlyto minimize this problem with slit position), especially in the blue. In order to minimize thedifferences between reference spectrum curvature and target spectrum curvature, it is bestto take both spectra at comparable sky position (airmass and hour angle) and the same slitorientation and positioning.

8.4. Extracting the Comparison Spectrum

In order to do the wavelength calibration, you need also to extract your comparison spectrum.Hopefully your chip was well aligned along columns or rows, so that there is not significantrotation which will cause shifts in rows/columns between the comparison and target spectra.If this is the case, you will need to extract BOTH comparison sources, do individualwavelength calibrations for each, and then interpolate the wavelength shifts as a function ofdistance between them.

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Extracting the comparison source spectra is done similarly to the target object spectra above,with a few exceptions. First, you need to store the extracted spectrum in a place other thanthe apall default name, by explicitly specifying a name. Second, because the comparisonsources are quite extended, you want to ensure that the “background subtraction” regionpicked is outside the area on the image occupied by the comparison spectrum. In thefollowing example of an apall call, the b sample keyword is specified to account for: (1)the image is 2x2 binned, (2) we are dealing with the right hand comparison spectrum inFigure 4, and (3) the background sampling region is made further away from the center ofthe comparison source to be in a “blank” part of the image:

apall bs8520b2 b sample=”-35:-25,40:50” output=bs8520b2.comp

The output image name will be bs8520b2.comp.ms.imh.

When the first graph is displayed by apall, ensure that you are on the correct place for thecomparison spectrum you want (compare the imtool position for example). If not, move theextraction to the correct place.

The graph showing the trace will show a lot of scatter, but this is a function of the few wellexposed places of spectrum (i.e., where the lines are) it has to work with. Therefore, it isrecommended that a low-order fit, say linear, be used for the trace.

8.5. Wavelength Calibration

For wavelength calibration of your spectrum, use the IRAF identify command. Before doingso, you need access to a data file containing a list of line identifications for the comparisonsources you used (Hg, Ne, or Hg+Ne). In Appendix A, an atlas of these sources, as well asa line list for IRAF is given. You should ask your TA for the location of this linelist file soyou do not need to type it in.

Invoke the identify command on your image, specifying the linelist file (in the example here,which has both Ne and Hg, the linelist is given the name idhehg.dat) specifically:

identify bs8520b2.comp coordlist=idhehg.dat

You will then be presented with a graph of the extracted spectrum, as in Figure 6a. Pick aline that you think you recognize, place the cursor over it, and type an “m”. The programwill ask you for the wavelength of the line and it’s name, which you should take from thelinelist. In the example, the feature at pixel 363 is the 4358.35 Aline of Hg, and you wouldreply to the query

4358.35 Hg

Do this again for at least one, but hopefully two other widely placed lines that you recognize.For example, the feature at pixel 154 is

5460.753 Hg(I)

and the feature at pixel 80 is

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5852.4878 NeI(6).

At this point, the program will attempt to fit all of the other lines that it can. Type an “l”to match other features with lines in your linelist. As soon as you do, you will be presentedwith a graph where the features are now shown in wavelength space, as in Figure 6b. Notethat the little dashes show the locations of expected features in your linelist; they shouldmatch the features in your spectrum.

Typing a “?” at any time will result in the presentation of a list of options for reworkingthe wavelength calibration. For example, use the “+” and “-” keys to step through theline identifications. If you screwed up your identifications, you can type an “i” to initialize.Typing an “f” will give rise to a graph as in Figure 6c, which shows how well the current fitof the dispersion works for your linelist. In general, the RMS residual should be less than 1and you should have no residual in the pixel to wavelength mapping more than a few pixels.You seen in FIgure 6c that the fit is worse in the blue. This is because there are fewer bluelines in this comparison spectrum to constrain the fit. You also see that a first order spline3function was used to to the fit. If you would like the fit to remove certain points, eitherremove the points you don’t like with the cursor and the “d” key, or type

:niter 10

to have the program iteratively throw out n-σ outliers, where the n is given by the low rejand high rej options. Make sure to type an “f” after each change in parameters. Use theh, i , j, k, and l keys to look at various representations of your fit. For example, “h” givesthe actual fit, instead of the residuals (Figure 6d), “i” gives you the fitting errors in termsof Doppler velocity shifts (Figure 6e), whereas “l” shows the non-linear component of thefit (which in the example of Figure 6e we can see there is some curvature in the dispersionsolution).

Type a “q” to leave the fitting window. Type another “q” to leave the program and createa database file with your solution. In the case here, the database file is

database/idbs8520b2.comp

and it contains the list of matched lines and the fitting parameters selected. This databasewill be needed to correct your target spectrum.

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Figure 6. Doing the wavelength calibration in IRAF.

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Chapter 15

The Astrovid 2000 Video Camera

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Astrovid 2000 Video Camera(Rev. August 06, 2007)

1. General Information

The Astrovid 2000 CCD video camera was purchased in early 1999 from Adirondack VideoAstronomy (www.astrovid.com). Its primary intended purpose is as the detector for thespeckle interferometry system, but its light weight and simple controls also make it ideal forestablishing a quick and direct video feed from the telescope. Note, however, that the videocamera should not be thought of as an integrating device since the maximum exposure timeis 1/60th of a second. The Astrovid is best applied to the viewing of bright objects (themoon, planets, bright stars) in real time, and the recording of high frequency phenomena(like speckles and seeing motion). An integrating CCD like the SBIG ST-8 is better for faintobjects. The Astrovid camera is designed for use with a standard 1.25” eyepiece mount. Anadapter has been constructed for the McCormick 26-inch refractor on the side of the flip-mirror system at the end of the tailpiece. A small portion of the total eyepiece field of viewcan be imaged with the Astrovid camera by moving the tailpiece flip mirror to its secondaryposition. The video output can either be directed to the high-resolution monitor soon tobe located in the dome room or directly into the McCormick laptop PC for the purpose offrame-grabbing.

The following manual explains how to set up the camera, use its controls to obtain an optimalimage, direct it’s video feed to the desired output device, and capture digital images in TIFFformat for later analysis.

General information about the camera and detector are summarized below. Note that theCCD in the Astrovid 2000 camera does not have square pixels.

Astrovid 2000CCD Sony HAD ICX038DLAChip Size 7.95 mm × 6.45 mmPixels 811 (horiz) × 508 (vert)Pixel Size 8.4 µm (horiz) × 9.8 µm (vert)Power Supply 12 V DCWeight 300 gOperating Temp 20 C to 55 C

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2. Setting Up the Camera

2.1. Mounting the Camera

The Astrovid 2000 CCD camera should have been mounted by the TA or the Observatory

staff in preparation for your lab. If it is not, use care in following these directions.

On the side of the McCormick 26” tailpiece, there is a mount with a threaded nut that

accepts a roughly 1-5/8” diameter threaded cylinder. This was designed to accept the SBIG

ST-8 CCD camera. The speckle system and Astrovid 2000 mount have been designed to fit

this mounting point as well.

The 1.25” mount for the Astrovid is a 2”-long brass cylinder with threading at one end and

a slit cut lengthwise through the other. This slit allows the camera barrel to be locked into

place with the aid of an aluminum ring clamp that fits around the mounting barrel. There

is an aluminum protector ring that fits over the threading when the mount is not is use; this

acts to keep the threads from becoming damaged.

To mount the camera to the tailpiece, first remove the thread protector ring from the brass

cylindrical mount. Next, align the threading with the mount extending from the tailpiece and

lock it in place with the threaded nut. Slide the camera barrel in and tighten the aluminum

ring clamp firmly about the barrel mount. This is accomplished by sliding the ring as far

toward the camera as is possible and tightening the thumb screw; the thumb screw should

be aligned roughly 90◦ from either lengthwise cut in the mount. Make sure that the camera

is oriented so that it is perpendicular to the underside of the tailpiece. Refer to Figure 1.

Note that the support brace seen in the images is not used with the video camera.

Figure 1. Camera mounting on the 26-inch tailpiece. Left: flip mirror systemwith open mount. Right: Astrovid camera mounted to flip mirror system

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2.2. Connecting the control box and power supply

The control box has a roughly 6-foot cable that acts as a communication line to the cameraitself. The box can be temporarily attached to the back end of the telescope during operation.Once the camera is in place, the two connectors at the end of this communication/video cableshould be inserted into the appropriate jacks in the back of the camera. There is a BNCconnector (refer to Figure 2 on the control box to which a coaxial cable can be attached.This is the video output, which can be directed to a monitor or computer.

Once all of the above steps are complete, the power line may be attached. At the presenttime, there are no free outlets on the power strip attached to the 26-inch telescope. Thereis, however, a white 12-Volt adapter attached which is not necessary for the use of theAstrovid camera. This can be unplugged and temporarily belayed. Since there are severalfree-hanging cables and the extra power supply is somewhat heavy, one should be careful toavoid getting hit by freely swinging objects. The black 12-Volt adapter that comes with thecamera should be plugged in to the now-empty spot on the power strip and the other endconnected to the control box. A red light on the camera itself will now be illuminated.

At the time this manual is being written, the camera control box and power supply are notattached to the telescope and must be connected and removed each time the system is setup. In the near future, however, a very long communication/video cable will be run from thetailpiece up the telescope tube to the axes of rotation, and then down to the main telescopecontrol panel. The control box and power connector will be located on the pier for easier use.When this layout is implemented, setting up the video system will simply involve attachingthe camera to the tailpiece, connecting the free-hanging cables, and turning on a displaydevice.

Figure 2. Cable connectors from left to right: RCA, BNC, F

2.3. Adjusting the Focus

Once the camera is in place, the tailpiece position must be adjusted to move the CCD intothe focal plane of the objective. Using the crank found on the pier, rotate the tailpieceadjustment bolt until the tailpiece position indicator is aligned with the marker labeled“speckle camera”. See Figure 3. This will bring the camera into rough focus. More refinedfocusing with the video camera is relatively easy because of the fast readout. The idealfocus may be checked by frame-grabbing images of unsaturated stars and checking the pointspread function (e.g., with the MIRA software).

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Figure 3. Adjusting the tailpiece for proper focus

3. Setting Up a Video Output Device

There are two possible video output devices: a TV monitor and/or PC. At the current time,the only monitor available is a large television that is kept in the observer’s room and mustbe carried into the dome room. In the near future, a high resolution monitor will be acquiredand most likely mounted on the pier in the dome room; this will make set-up very simple.

To use the television as an output device, one simply needs to attach the f-type connectoron the coaxial cable to the “ANTENNA” port of the TV.

To use the McCormick laptop PC as a display device, first make sure that the “VideoportProfessional” PC card is inserted into one of the two PC slots on the side of the computer.There is a connector that plugs directly into this and at the other end accepts an RCA plug.An RCA-to-F-type male connection adapter should be attached to the RCA connector. Tothis adapter should be attached a small female-to-female F-type connection adapter. Thecoaxial cable from the camera control box can be attached to this. Use of the frame-grabbingsoftware for viewing and capturing the video output is discussed in a subsequent section.

When the new high resolution monitor and long communication cable are in place in thedome room, the monitor will be set up semi-permanently to receive video feed in the followingmanner. The control box will live on the pier and the coaxial video feed will be attachedto a “T” splitter which will also be attached to the pier. One of the two outputs from thissplitter will be attached to the monitor so that all one needs to do to view the camera outputis attach the camera to the tailpiece, turn on the power, and turn on the monitor. The otheroutput from the splitter will have a free cable which can be attached to the PC card in thelaptop if desired. In this way, the monitor can be used for easy viewing while the laptop canbe used for frame grabbing.

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4. Camera Controls

The Astrovid 2000 system consists of a control box, power adapter, video cabling, and thecamera itself. In this section we will concentrate on the control box.

There are 3 controls that can be adjusted to help produce an optimal image.

1. The Shutter Speed controls the length of each individual video frame exposure. Thereare 2 OFF positions and 8 ON positions with differing shutter speed. The longestshutter speed is 1/60 sec; note that this is not long enough to allow direct videoimaging of low surface brightness objects.

2. The Gain controls the amount of signal amplification. The gain is off when the indicatorpoints to the left and is at its maximum when pointing to the right.

3. The Gamma control adjusts the contrast in the image. By using various combinationsof SW 1 and SW 2 in their 2 positions, varying contrast levels can be chosen.

The goal is to adjust the various controls in such a way as to produce an image with thebest signal-to-noise, contrast, and dynamic range for your application. Increasing the gainresults in an amplification of the signal in all pixels: in addition to amplifying the pixels ofinterest, the overall noise in the image is also amplified. When possible, it is preferable toproduce a brighter image by decreasing the shutter speed rather than increasing the gain.The result will be a cleaner image.

The following is a summary of the various possible control settings:

Shutter Switch

Setting Time (sec)0 1/10,0001 1/4,0002 1/2,0003 1/1,0004 1/5005 1/2506 1/1257 1/608 off9 off

Gain control

Clockwise Decrease gainCounter clockwise Increase gain

Gamma Setting

SW 1 Up Gamma = 1.0 Normal ModeSW 2 Don’t careSW 1 Down Gamma = 0.45 Medium ContrastSW 2 UpSW 1 Down Gamma = 0.2 High ContrastSW 2 Down

5. Centering the Image on the CCD

Getting the desired object centered in the video camera CCD can unfortunately be a bitchallenging. Since the chip is small, it sees only a small fraction of the total field visible in

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the eyepiece. The CCD field of view is, however, fairly well centered in the eyepiece field ofview. To get the object of interest to appear on the display device, first find it by eye usingthe eyepiece. Get it centered as much as possible in the field of view. Now move the flipmirror on the tailpiece to redirect the light into the camera. If the object does not appear onthe monitor, try adjusting the gain and exposure time. If it still does not appear, you mayhave to make some small adjustments to the pointing of the telescope to move that sectionof the image onto the chip.

6. Capturing Images With the McCormick Laptop PC

To capture digital images from the Astrovid 2000, first connect the coaxial cable to thesequence of adapters that lead to the PC card in the laptop computer. Run the programcalled “Image Wizard”.

From the “File” menu, select “Scan...”. Alternatively, there is a shortcut button in the lowerleft corner of the control panel that issues the same command. Select “Acquire” from thebox that pops up. You should now see a window which looks something like that shownin Figure 4. Make sure that “Greyscale” is selected in the “Picture” box and that “1/1”is selected in the “Size” box. You should see the live video output from the camera in thepreview box. Note that the capture rate through the PC vie “Acquire” is not as fast asthe live video rate seen through the monitor (i.e. the PC does not show every integrationframe). When you’re ready to capture an image, click on the “Capture” button and then on“Ok”. The image you’ve just captured should appear in the main window of the program.Repeat this process to capture further images.

Figure 4. Image Wizard TWAIN acquire window

Be conscious of the number of open windows on the desktop. Capturing too many imageswithout saving may result in memory problems. Desirable images should be saved to disk

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periodically and their windows should be closed unless they are needed for reference. Imagesshould be saved in TIFF format. Most image analysis and manipulation programs can readTIFF images. Also be conscious of the amount of available hard drive space on the laptop.Data should be saved on the laptop only temporarily. It is preferable to transfer image datato another disk when possible.

You may want to capture and co-add a series of images. Note that the rate of image captureis dependent on the bus transfer rate and processor speed of the computer, but each capturedframe is of the integration length selected on the control box. To co-add a series of capturedimages, select “Averaged Capture...” from the “Video Capture” line in the “File” menu. SeeFigure 5. You should see a window similar to that in Figure 6. You can specify the numberof frames to be captured as well as the division factor. If you want to simply accumulateframes without averaging, you would leave the “Divide Result by: ” box set to one. Forcomplete averaging, both boxes should contain the same number.

Figure 5. Image Wizard File menu and Video Capture selections

Figure 6. Image Wizard video averaging

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7. Shutting Down

Please leave the Astrovid 2000 and the telescope as you found them. If the camera wasinstalled when you arrived at the telescope, then leave is installed. At the end of the night,be sure to shut off the TV monitor and/or laptop. Disconnect the power to the video camera,but leave it attached to the tailpiece. Either a TA or the Observatory staff will remove itwhen necessary.

If you installed the Astrovid camera system, please uninstall and store the camera in theequipment cabinet where you find it.

Finally, re-stow the telescope in the standard way.

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Chapter 16

The Astronomy Library andAstronomical Literature

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The Astronomy Library and AstronomicalLiterature

(Rev. August 09, 2011)

1. The Astronomy Library

The Astronomy Library is one of the departmental libraries associated with the Science andEngineering Library. It is located in the Astronomy Building in Room 264. It is accessiblevia key access only.

The Astronomy Library holds material supporting graduate academic programs as well asadvanced research in astronomy and mathematics. It contains more than 13,000 books and265 journal and serials subscriptions. Astronomy and Mathematics materials are shelvedas separate collections. Unbound journal issues are shelved alphabetically by title. Boundjournal volumes are shelved by call number.

The Astronomy Library houses the specialized Astronomy books, conference proceedings,observatory reports, periodicals (journals) and reference books. Ph.D., M.A., and under-graduate Senior theses generated by the Astronomy Department are also displayed in thelibrary. Some general astronomy books are kept in the larger Science & Engineering Libraryin Clark Hall, and some older journals and books are now stored in the Ivy Stacks wherethe air quality is well controlled.

The most recent volumes of periodicals are kept on a special shelf in the library near thelibrarian’s desk. Reserve books are located on a shelf behind the librarian’s desk. The mostrecent book arrivals are displayed on the bookshelf next to the new periodicals.

Do not re-shelve any materials which you use in the library. Please leave themon the counter in front of the librarian’s desk.

∗No food or drink are allowed in the Astronomy Library!∗ Food attracts pests whichthen feed on the paper in the library’s volumes. Failure to comply with this restriction willresult in loss of library privileges.

For more information on the Astronomy Library, check the World Wide Web athttp://www.lib.virginia.edu/science/scilibs/astr-lib.html and for more details selectCollections from the first web page.

1.1. Reference and Information Services

The Astronomy Library provides instruction in the use of both electronic and traditionalreference tools, in addition to helping you with specific reference questions. You may contact

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Beth Blanton-Kent for personal assistance: (e-mail: blanton@virginia.edu), call 924-6837, orchat on IM to selblanton.

2. Guide to Astronomical Literature

For astronomers, professional and amateur alike, information is obtained from a varietyof sources. Here is a brief introduction to these sources, their use and utility. A list ofthese sources would include journals, texts, books, catalogs, atlases, almanacs, conferenceproceedings, observatory reports, emphermides, charts, magazines, databases, etc. Thefollowing is a general description of each type of reference, its particular use and listsof the more prominent examples. You will see that astronomers utilize a diverse set ofreferences both to carry out investigations and to keep abreast of current research. Athorough understanding of their use is essential to productive work.

2.1. General Guides

Two old but very good guides to astronomical literature are:

Seal, Robert A. 1977, A Guide to the Literature of Astronomy, Littleton, Colo., LibrariesUnlimited. (Z 5151.S4)

Kemp, D. A. 1970, Astronomy and Astrophysics; A Bibliographic Guide, London, MacDonaldTechnical and Scientific; distr. Hamden, Conn., Archon Books, Shoestring Press, Inc. (Z5151.K45)

The first book in particular contains helpful information for finding your way around anAstronomy Library. Be forewarned: Books dealing with astronomy are assigned Library ofCongress numbers by librarians not astronomers.

2.2. The Age of the Computer

The advent of the World Wide Web (WWW) has enabled access to many online electroniccomputer databases. Most libraries now have computerized lists of their holdings (e.g., theUVa Libraries) and provide access to other libraries. Books can even be requested andreserved electronically. Literature searches can now be effectively accomplished sometimespurely by computer. Some journals, like the Astrophysical Journal Letters, are now acceptingmanuscripts and displaying refereed papers electronically in addition to the usual paper copy.However, it will be a while before we have no need for the reliable hardcopy of our favoritejournals.

For lists of astronomical databases you can begin with the following WWW addresses:http://www.astro.virginia.edu/www/ orhttp://www.lib.virginia.edu/science/scilibs/astr-lib.html

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2.3. Periodicals/Journals

Journals are periodical (weekly to yearly) softback publications designed to give the readerup-to-date knowledge of the astronomical world. One can loosely subdivide journalsinto three categories: professional journals, popular astronomy magazines, and generalscience journals. Professional journals contain technical research reports. This is wherean astronomer learns of current advances in all fields of astronomy and where a researcherpresents his/her work to the scientific community. Articles published in professional journalsnormally follow strict editing guidelines, are abstracted and heavily references, and have beenrefereed before publication. General science journals also contain research reports, but covermany scientific fields. Popular astronomy magazines attempt to bring a larger audience theexcitement of current astronomy and space research and explain to the educated laymanthe sometimes exotic objects and processes which populate the universe. Also, popularastronomy magazines present sky charts, updates on visible planets, eclipses, comets, etc.,articles of interest to amateur telescope makers, and serve as an advertizing medium forastronomy related items. Following is a list of the more important journals.

Astrophysical Journal (ApJ) - University of Chicago PressThis is the premier professional journal. Published twice monthly it contains research articleson all subfields of astronomy Articles containing large amounts of data are published in theAstrophysical Journal Supplement Series about five times yearly.

Astronomical Journal (AJ) - American Institute of PhysicsEqual in stature to the Astrophysical Journal, the Astronomical Journal is published monthlyand contains fewer articles. Content is similar to ApJ.

Monthly Notices of the Royal Astronomical Society (MNRAS)The primary British professional journal, and the oldest continuous astronomical publication.Format and style is similar to ApJ.

Astronomy and Astrophysics (AAp) - Springer-VerlagThis is the primary European research journal and contains articles on all subfields ofastronomy by primarily European astronomers. It also has a supplement series.

Science - AAASA weekly journal containing articles in all scientific disciplines, but emphasizing biology.This journal also published articles and editorials concerning science policy which are ofinterest to the astronomer.

Nature - MacMillan JournalsVery similar to Science, published in Great Britain. Weekly.

Science NewsA weekly science newsletter geared toward the scientist and science oriented layman; it isnot a research journal. Major scientific discoveries and results of space missions reach herelong before they appear in professional journals. Science News is the “Time Magazine” ofthe scientific world.

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Sky and Telescope - Sky Publishing CompanySky and Telescope has no peer as a popular astronomy magazine and is read by mostprofessional astronomers as well. No other periodical appeals to so broad a range of interestsin astronomy.

AstronomyA recent (compared to Sky and Telescope) popular astronomy magazine published monthly,Astronomy is designed more for the amateur. Feature articles tend to have a ’gee whiz’ style;there are many colorful illustrations. The Astronomy News section is especially useful.

There are dozens of additional professional journals (the astronomy department receivesabout 25 different journals). Because the time between completion of a paper and publicationin a journal can be longer than a year, astronomers rely increasingly on preprints which aresent out when a paper is completed (before or after refereeing). Distribution of preprintsoccurs informally among researchers and astronomy libraries.

2.4. Conference Proceedings

Astronomers frequently attend symposia, conferences, meetings, etc., and deliver researchpapers. The collected papers of such a meeting are a very important source of information.Their importance lies in the fact that most subfields of astronomy have no text which givesup-to-date knowledge of that subfield. A conference organized on a particular topic providesan excellent summarization. Some of the most significant conference proceedings are theIAU symposia and colloquia (blue, cloth covered volumes).

2.5. Observatory Reports

All major and many minor observatories and astronomical research institutes publishresearch reports describing the activities at that institution. Frequently they are entitled“Publications of so-and-so Observatory”. In the early days of astronomical research (prior toWWII) observatory publications were the primary method of disseminating research results.They have subsequently been supplanted by the professional journals. Today the publicationsof many major observatories contain fewer research reports, and deal with staff, instrumentupgrades, and computer programs. There are two publications of particular utility:

Bulletin of the American Astronomical Society (BAAS)This publication, available to members of the AAS, contains observatory reports whichdescribe the ongoing research programs of that observatory. Published on an annual basis.

IAU CircularsDistributed by the Central Bureau for Astronomical Telegrams, located at theHarvard-Smithsonian Astrophysical Observatory, these cards are designed to call attentionto recently discovered and/or transient phenomena so that world observatories can quicklyplace them under observation. Frequent items are: variable star outbursts, new comets,supernovae in external galaxies, and enhanced activity in active galaxies (QSO’s).

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2.6. Review Literature

In addition to conference proceedings, review articles are the other major source ofinformation which summarizes a topic or subfield of astronomy. Below is a short list ofreview literature. Frequently an “invited lecture” to a conference will be a review and isprinted as the first paper in the conference proceedings. Occasional monographs by seniorastronomer provide excellent reviews.

Annual Review of Astronomy and AstrophysicsPublished since 1963, this journal contains about 15 essays on various topics selected by aneditorial board of leading astronomers. Essentially non- mathematical technical articles ofabout 30 pages in length. Extensive references given with each article are very useful to thestudent.

Comments on AstrophysicsThis small publication, published about 3 timers per year, contains technical (andmathematical) reviews, normally 3 papers to an issue.

Scientific AmericanThe major popular science review magazine, it is published monthly invariably with at leastone astronomy related article. It is geared for the scientist and very educated layman;contains about 8 twenty page papers illustrated with colorful diagrams and photos, oftenwritten by an eminent astronomer.

2.7. Abstracts

There is one major index to astronomical literature; Astronomy and Astrophysics Abstractspublished semi-annually. It contains the abstracts of all articles published in the majorjournals, exactly as those abstracts appear in the journal. Entries are divided into 108separate categories by subfield. In addition to research and review articles, conferenceproceedings, books, texts, atlases, etc. published during the 6 month period covered bythe volume are listed. There are two indexes; by author and subject (not by title). Thesubject index is good but not comprehensive. Since these abstracts are always about a yearbehind, an offshoot has appeared since 1976, “Astronomy and Astrophysics Monthly Index”.This contains an author and title index but no subject index.

2.8. Almanacs, Data Books, Handbooks

This category of the literature can loosely be defined as sources of data which the astronomerneeds to successfully complete observations.

The Nautical AlmanacAn indispensable text for every observatory; the Nautical Almanac is published yearly by theU.S. Naval Observatory. It contains voluminous information on mundane, daily, astronomicalphenomena like sunrise, sunset, moonrise, positions of the planets and their satellites as well

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as formulae for calculating the positions of celestial objects. Tables give current epochpositions of bright stars, galaxies, and radio sources.

Astrophysical Quantities by AllenThis text represents the current (publication date) state of knowledge about celestial objects.Divided into many categories, it gives such data as the masses, sizes, distances, and orbitalperiods of the planets, lists of the brightest and nearest stars, temperature and luminositiesof various stellar types and so on. The quickest way to find a particular value in astronomyis pick up this book. The last edition was published in 1973 and is becoming outdated.

Astrophysical Formulae by LangThis text contains hundreds of astronomical and physics formulae and complements Allen’swork.

Astrophysical Data (1991) by LangThe latest most up-to-date listing of astrophysical data. In two volumes.

2.9. Charts and Atlases

Reference works in this category are an essential tool for observational astronomy foramateurs and professionals alike. An astronomical atlas is a representation of the sky or someobject in the sky (esp. the moon) and consists of either photographs, maps or overlays. Manyatlases are “all sky” maps (e.g., Palomar Observatory Sky Survey, SAO atlas), some mapout a particular type of object (AAVSO Variable Star Atlas), others present a compilationof objects (Hubble Atlas of Galaxies, MK Atlas). All of these works aid astronomers inpreparing and subsequently reducing observations. The advent of the space age has openedup new areas of the spectrum for observation; here atlases help identify objects found to beemitting in the ultraviolet, infrared, etc. Some major works are:

Smithsonian Astrophysical Observatory Atlas (and Catalog)This reference contains 152 charts covering the entire sky on which stars to about 10thmagnitude and many non-stellar objects are plotted. Designed to be used in conjunctionwith the SAO Star Catalog (described in the next section).

AAVSO AtlasSimilar to the SAO atlas, variable stars brighter than 9.5 mag. (visual), and amplitudesgreater than 0.5 mag. are plotted using 1950.0 epoch at 4’/mm.

Norton’s 2000.0 Star AtlasPerhaps the most popular star atlas for amateur astronomers. Formerly Norton’s Star Atlas.

The MK AtlasA photographic atlas depicting the standard stellar spectral classification system.

Uranometria 2000.0A photographic atlas of the Northern Hemisphere (Vol. I) and Southern Hemisphere (Vol.II), for stellar objects with magnitudes less than 9.5.

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Palomar Observatory Sky Survey (POSS I): Photographic atlas of the Northern Hemisphere.

European Southern Observatory (ESO): Photographic atlas of the Southern Hemisphere.

New Palomar Observatory Sky Survey (POSS II): Photographic atlas of the NorthernHemisphere.

SERC-EJ: Equatorial atlas

The major sky surveys are listed in Table 2.8 of Mihalas and Binney’s Galactic Astronomy,and some major galaxy atlases are listed in Table 2.7 of that reference.

2.10. Catalogs

As atlases are an astronomer’s right hand, catalogs are his/her left hand. Almost all workin astronomy prior to this century consisted of creating catalogs. The first astronomerscataloged the positions of stars, then later “brightness” (magnitudes). People like Herscheland Messier plotted non- stellar objects. Not until the final decades of the 19th century didphysics oriented researchers begin investigating astronomical problems (classical mechanicsexcluded). Later, after the techniques of spectroscopy and photography were developed, itwas possible to pursue the analysis of the properties of celestial objects. A list of someimportant Astronomical Catalogues is given in Table 2.6 of Galactic Astronomy. A usefulrecent stellar catalogue is the Sky Catalogue 2000.0 which lists the observed properties ofstars down to magnitude 8.0. It is published in two volumes, and the second volume describesclasses of objects, e.g., types of binaries.

2.11. Publisher’s Series

There are two series of books which deserve special mention:

Stars and Stellar SystemsAn eight volume set published by the University of Chicago Press which was designed tocover all aspects of astronomy. Now mostly out-of-date. Titles are:Telescopes (1960)Astronomical Techniques (1962)Basic Astronomical Data (1963)Galactic Structure (1965)Stellar Atmospheres (1960)Nebulae and Interstellar Matter (1968)Stellar Structure (1965)Galaxies and the Universe (1976)

Astrophysics and Space Science LibraryProduced by D. Reidel Publishing Company, this series now contains over 80 volumescovering diverse topics in astronomy. Individual volumes have a variety of formats; manyare conference proceedings.

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2.12. Observational Astronomy

Observational Astronomy by D. Scott Birney (1991). Up-to-date. Intended forundergraduate students.QB 145.B52

Modern Technology and its Influence on Astronomy edited by J. V. Wall and A. Boksenberg(1990). Selected articles on a variety of telescope designs from optical to radio.QB 84.5.M63

Data in Astronomy by C. Jaschek (1989). Discussion of types of data and ways in whichthey are archived.QB 51.3.E43J37

Observational Astrophysics by P. Lena (1988). An up-to-date text. Intended for graduatestudents. Description of observing techniques, detectors, and data analysis procedures.QB 461.L46

Astronomical Techniques by C. R. Kitchin (1988). Good undergraduate text. Descriptionof detectors and a variety of imaging techniques. Recommended reading.Q13461

Astronomy: Principles and Practice by A. E. Roy and D. Clarke (1988). Goodundergraduate level text.QB 43.2

Astronomical Observations by G. Walker (1987). An up-to-date text. Intended for graduatestudents.QB 86.W35

Astronomical Techniques ed. by W. A. Hiltner (1962); Vol. II of Stars and Stellar Systems.An extensive text which gives a detailed description of optical observational astronomy(photometry, spectroscopy, photography, measurement and reduction of observations). Itis one of the two basic texts in the field, but it was published almost 30 years ago and anupdated version is needed.QB 86.H5 (Ast)

Basic Astronomical Data ed. by K. A. Strand (1963); Vol. III of Stars and StellarSystems. This volume gives the definition and calibration of the quantities which are usedto characterize celestial objects.Recommended reading: Chapters 8, 9, 11, 12, 13.QB 801.S75 (Ast)

The Astronomical Telescope by B. V. Barlow (1975). An excellent 200 page text.Recommended reading: Chapters 3, 4, and 7 (read during first week of semester).QB 88.B37 (Ast)

Observation in Modern Astronomy by D. S. Evans (1968). A mostly descriptive text; it isan excellent supplement to Norton’s Atlas if you feel that the Atlas is too concise.

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Recommended reading: Chapters 1, 2, and 3.QB 64.E86 (Ast)

Tools of the Astronomer by G. R. Miczaika (1961). Mostly descriptive, but a bit out-of-date. Recommended reading.QB 86.M5 (Ast)

Methods of Experimental Physics Volume 12, Part A: Optical and Infrared, ed. byN. Carleton (1974). A comprehensive text. It is 600 pages in length and consists of aset of review articles on topics in observational techniques. Examples: Photomultipliers,Characteristics of Photographic Plates, Television Systems. Intended for graduate students.QB 465.A8 pt.A (Ast)

2.13. Data Analysis

Practical Astronomy With Your Calculator by P. Duffett-Smith (1979). Topics includetime, coordinate system transformations, orbits of planets, orbits of planets, eclipses, andspherical astronomy.QB 62.5.D83

Mathematical Astronomy With a Pocket Calculator by A. Jones (1978). Most of theprograms described deal with spherical astronomy. This will be useful for computing currentepoch coordinates, and reducing radial velocities to heliocentric values.QB 47.J66 (Ast)

Data Analysis For Scientists and Engineers by S. Meyer (1975). A guide to scientific datacollection, reduction, and analysis. Also contains extensive material on probability.QA 276.M437

Data Reduction and Error Analysis for the Physical Sciences by P. Bevington (1969).Discussion of errors, probability, curve-fitting, least squares, and simple statistical tests.QA 278.B48

2.14. Specific References Related to Observational Astronomy

Telescopes

The Astronomical Telescope by Barlow, especially Chapters 4, 5, 6.Tools of the Astronomer by Miczaika, Chapter 3, 4.

Photometry

Astronomical Photometry by Henden and Kaitchuck, the entire bookTools of the Astronomer by Miczaika, Chapter 5Astronomical Techniques by Hiltner, Chapters 6, 7, 8, 9

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Methods of Experimental Physics by Carleton, Chapters 1, 2, 9Basic Astronomical Data by Strand, Chapters 9, 11, 13Astronomical Papers Dedicated to Bengt Stromgren, a symposium held in May 1978. Mostlytechnical papers on the application of photometric observations. QB 1.A88Introduction to Astronomical Photometry by Golay, Astrophysics and Space Science Library,Vol. 41 (1974). Graduate level text; not easy reading. QB 135.G64Problems of Calibration of Multicolor Photometric Systems, Workshop proceedings held inMay 1979. Pages 83 – 102 give a review of the DDO photometric system.

Spectroscopy

Tools of the Astronomer by Miczaika, Chapter 6Basic Astronomical Data by Strand, Chapter 8Methods of Experimental Physics by Carleton, Chapter 10Astronomical Techniques by Hiltner, Chapters 2, 3, 4, 12

Spectral Classification

“Fundamental Stellar Photometry for Standards of Spectral Type on the Revised System ofYerkes Spectral Atlas,” Ap. J, 117, 313 (1953), H. L. Johnson, W. W. Morgan.

“Classification of Stellar Spectra,” Volume 3, in Stars and Stellar Systems: Basic Astronom-ical Data, 1963, Philip C. Keenan

Henry Draper Catalogue, Harvard Annals, Volumes 91-99.

“The Spectroscopic Absolute Magnitudes and Parallaxes of 4179 Stars,” Ap. J., 81, 187(1935), W. S. Adams and A. H. Joy, M. L. Humanson, A. M. Brayton.

An Atlas of Stellar Spectra, Morgan, Keenan, Kellerman (1943).

An Atlas of Low Dispersion Grating Stellar Spectra, Abt, Meinel, Morgan, Tapscott (1968).

Atlas for Objective Prism Spectra Bonner Spectral Atlas I, W. C. Seitter (1969).

An Atlas of Spectra of the Cooler Stars Types G, K, M. S, and C, P. C. Keenan, R. C. McNeil(1976).

A Multiplet Table of Astrophysical Interest C. E. Moore, 1945, Revised Edition, PrincetonContributions No. 20. see also: Atomic Energy Levels, Vol. I, 1949; Vol. II, 1952; Vol. III,1958; National Bureau of Standards, Circular 467.

Lines of Chemical Elements in Astronomical Spectra P. W. Merrill, 1958, Carnegie Inst. ofWashington Publ. 610.

The Solar Spectrum 2035A to 8770A C. E. Moore, G. H. Minnaert, J. Houtgast, NationalBureau of Standards Monograph 61.

The Ultraviolet Spectra of A- and B-Stars, O. Struve 1939, Ap. J., 90, 699.

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Revised MK Atlas for Stars Earlier than the Sun Abt, Morgan and Tapscott, 1977 (referencedin the 1976 ”Atlas of Spectra of the Cooler Stars”).

Bonner Spectral Atlas Part 2.

Revised MK System, P. C. Keenan and R. E. Pitts 1980, Ap. J. Suppl., 42, 541.

Photography

Miczaika, Chapter 2Carleton, Chapter 5Hiltner, Chapters 15, 16Modern Techniques in Astronomical Photography, in the proceedings of an ESO workshopheld in May 1978.AAS Photo-Bulletin, an irregular publication devoted to photographic procedures. Thelatest cumulative index is on reserve.Kodak publications on photographic plate characteristics and plate cutting.

Optics

Miczaika, Chapter 1Barlow, Chapter 3Fundamentals of Optics by Jenkins and White. QC 355.2.J46Fundamentals of Physics by Halliday and Resnick, Chapters 35 to 39Physics by Tipler, Chapters 25, 26, 27.

Spherical Astronomy

Spherical Astronomy by Smart (1949). QB 145.S6The Nautical Almanac

General Astrophysics

Introduction to Astronomy and Astrophysics by Smith and Jacobs. QB 47.B47Outline of Astronomy by Voigt, 2 volumes. Several sections of this text deal with techniquesas well. QB 62.V6413

Advanced Techniques

Instrumentation in Astronomy, Volumes I, II, III. QB 86.I58*Scientific Research with the Space Telescope (an IAU Symposium). QB 88.S35Auxillary Instrumentation for Large Telescopes, ESO/CERN conference (1972).QB 86.E18

Radio Astronomy

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The Invisible Universe by G.L. Verschuur (1974). QB 475.V47Radio Astronomy by J.D. Kraus (1986), Cygnus-Quasar BooksGalactic and Extragalactic radio Astronomy by G.L. Verschuur and K.I. Kellermann (1988),2nd edition, Springer-VerlagAn Introduction to Radio Astronomy by B. F. Burke and F. Graham-Smith (1997),Cambridge University Press

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Appendix A

Using IRAF on a UNIX Workstation

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Using IRAF on a UNIX Workstation(Rev. August 06, 2007)

1. Starting IRAF

Once you have logged in to one the Department of Astronomy’s UNIX workstations, youwill be able to use the IRAF software package to reduce and analyze your CCD data. Thecomputer account you are using should already be set up to run IRAF. If it is not, see thedepartment’s computer guru, Howard Powell, or your TA for help.

To begin using IRAF, do the following:

1. Type cd iraf to move to the iraf setup directory.

2. Type cl to begin IRAF (cl means command language).

3. In another window, type: ximtool &. This will start an image tool window.

4. (To exit IRAF, type logout, or lo for short.)

Once you have started IRAF, the prompt in the IRAF window will always be two lettersfollowed by a “>”. For example, the prompt will be cl> after start up. These letters changedepending on which IRAF package was last loaded. Note that once an IRAF package isloaded, you may access tasks within that package even if other packages have been loadedafterwards.

Note that it is not possible to give a thorough treatment of the IRAF package here, butonly an introduction. To learn more about any particular task taskname, you may type helptaskname at the IRAF prompt. To find out which tasks have been loaded at any particulartime, you may type a “??” at the IRAF prompt. IRAF is a huge program with many tasksand add-on packages. Only a small subset of the entire IRAF behemoth is covered here.

2. FITS vs. IRAF format

IRAF will, by default, convert all images into a standard format only compatible with IRAF.It will work with FITS images, although this does entail some risk as the FITS kernel isrelatively new. All the commands described below are designed to work with FITS images.You simply replace ”.imh” and ”.pix” with ”.fits”.

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By default, IRAF will convert your image from fits to IRAF when any operation is appliedot it. Suppose your images have names like “ccd117.fits”. Any operation will convert theimage into the standar IRAF format “ccd117.imh” and “ccd117.pix”.

In this context, “.imh” is the suffix specifying the IRAF file (meaning “image header”).At this point it is necessary to make brief mention of the IRAF file format. IRAF wasdeveloped at a time when disk space was hard to come by but CCD images had alreadybecome reasonably sized. It was common at this time for there to be a “large-sized” diskshared by all users in a networked environment. The philosophy of IRAF was a compromisebetween the fact that users would want to have their images arranged within their personaldirectory structure, and the problem that these disk areas were usually too small to handlethe images. Thus, each IRAF image has two files:

1. A “.imh” image header file that is small and that contains header information aboutthe image (dimensionality, array size, number of bytes per pixel, etc.), as well as apointer to where the real pixel data is to be found, and

2. The “.pix” file which contains the meat of the image, the large file of pixel values.

Unfortunately, in spite of the fact that disks are much larger now, the versions of IRAF priorto 2.11 are wed to this dual file format and it is important to be mindful of it. Two rulesmust always be followed when dealing with IRAF images:

1. All operations you do with IRAF tasks must act on the “.imh” images (IRAF keepstrack of the real manipulations with .pix files), and

2. Never perform UNIX operations on IRAF images that will change the directorylocations of the “.imh” and “.pix” files. In general, it is not a good idea to do anyUNIX operations on IRAF files; however, most UNIX operations (e.g., mv, cp, rm)have IRAF counterparts (e.g., imrename, imcopy, imdelete) that act on the coupledIRAF files. Always use the IRAF tasks for operations on images.

You may want to leave images in FITS format so that they can be operated on by otherprograms, such as IDL. To do this you need to type:

cl> reset imtype="fits"

cl> flpr

cl> reset imextn=".fits"

You can also add the reset commands to your login.cl program to have it be the default.

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3. Common IRAF Tasks

We now briefly turn to the most commonly used IRAF tasks that you will want to use.Again, read the help files of these tasks to learn the full capabilities. For each IRAF task,there are two sets of associated parameters: hidden parameters which, once set, remain helduntil changed explicitly, and unhidden parameters which must be set every time the task isinvoked. The list of unhidden and hidden parameters for a task may be seen by typing

cl> lpar taskname

The hidden parameters are the ones shown in parentheses when you do an lpar command.Unhidden parameters may be typed on the command line, but if not included there, you willbe asked for them by the program. For example, to display an IRAF image in your imtoolwindow, use the display task:

cl> display ccd117.imh

Note, if you simply type

cl> display

you will then be asked

image to be displayed ():

Anything written in the parentheses after such a question is considered a default, and canbe accepted with a simple <cr>. The default is generally related to the last time yousuccessfully invoked the same command. For example, if you had previously display animage “ccd116.imh”, you would have been asked

image to be displayed (ccd116.imh):

Hidden parameters may be changed in several ways. At any point you may change a hiddenparameter at the IRAF command line, as in the following example:

cl> display.fill=yes

In this example, the hidden parameter “fill” of task display is set to “yes” and will remainso until changed again. The display.fill option tells IRAF whether to squeeze down an imageto fit it entirely into the full display region of ximtool if set to yes, or to display only thecentral portion of the image with a 1:1 mapping of pixels into the 512x512 ximtool displayarea.

When many parameters need to be changed for a task, use the epar command, e.g.:

cl> epar display

which will then bring up the full menu of both hidden and unhidden parameters. Use the<down> or <up> arrows to examine the parameters. To change one, move to it with the<up> or <down> arrow, type in the new value, then move on. You do not need to type a

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<cr> with each new entered value. When you are finished editting parameters, exit with acontrol-<d>.

Alternatively, you could have changed the hidden parameter at the invokation of thecommand display:

cl> display ccd117.imh fill=yes

but note that in this case the hidden parameter is changed only for this single invokationof the display command, and will revert back to the default fill=no when the command isfinished, unless it had already been previously set to fill=yes.

Here is a list of other IRAF tasks you may find useful (note: you need only type an IRAFcommand to the point that the typed letters specify a unique IRAF task):

• imdelete - delete a “.imh” file and its associated “.pix” file

• imcopy - make a copy of the image

• inrename - rename an image, or move it to a new directory (specify as the new namethe directory path and file name)

• imarith - do mathematical operations between images of similar dimensions or betweenan image and a constant scalar value

• imcombine - combine (average, median, mode) a set of images of the same dimension

• imhead - give information about an image

• implot - plot columns or rows of an image

• imhistogram - plot a histogram of the pixel values in an image

• imstatistics - calculate statistics of an image

• minmax - tell the minimum and maximum values in an image

• pcol, pcols - plot column or columns of an image

• prow, prows - plot row or rows of an image

• contour - make a contour plot of an image

• surface - make a surface plot of an image

• imexamine - a more sophisticated version of implot that interacts with the imtooldisplay of the image and with many useful facilities, including those of implot, contour,surface, imstatistics, etc.

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Finally, a word on image sections. Any of the above IRAF operation may be performed onimage sections. In IRAF, the x-dimension of an image is specified as columns, and the y-dimension is specified as rows (or lines), and described always in the specific order [columns,rows]. For example, if you do an imhead on an image, you will get back the dimensions ofthe image as, e.g., [2048, 2048]. But you may also operate on specific sections of imagesby specifying rows and columns explicitly, and with a “:” as the delimiter for ranges. Forexample, to display only columns 101 to 200 and rows 301 to 400 of image ccd117.imh, youwould type

cl> display ccd117.imh[101:200, 301:400]

and to copy line 233 of image ccd117.imh into a separate image, ccd117.233.imh

cl> imcopy ccd117.imh[*,233] ccd117.233.imh

where here the “*” wildcard specifies all columns. In most operations of IRAF, the “.imh”is assumed, so that

cl> imcopy ccd117[*,233] ccd117.233

would operate identically to the above command.

4. Image Reduction in IRAF

This section of the IRAF manual is intended to provide students with a standard methodfor reducing CCD images. Please note that the manual is not exhaustive. For a thoroughtreatment of the subject, refer to Phil Massey’s A User’s Guide to CCD Reductions withIRAF on the NOAO web page or the printed version in Kerchoff 313.

The images that you will obtain from the department CCD’s are not perfect. They containvarious systematic effects which distort the images. The removal of these systematic effects,achieved by comparison with calibration images, is the process of reduction. This sectionwill detail how to remove the overscan, trim an image, subtract the bias, subtract the darkcurrent, divide by the flat field, and divide by the illumination. The result should be a niceclean flat image.

The entire process of reduction hinges upon your having a set of “calibration images.” Theseimages, itemized below, are what you will use to calibrate the object images—the picturethat you want to process. Read this list before observing.

Bias Frames: frames taken with a zero exposure time with the shutter closed. You shouldhave 10 of these for each night that you observed.

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Dark Frames: frames taken with the shutter closed. These monitor the induce thermalcurrent of the chip. The ST-8 and smaller CCD’s will take darks automaticallyat your request. These are thermo-electrically cooled CCD’s and the dark currentis substantial. You will need to actively take dark frames for each combination oftemperature and exposure time. The Fan Mountain CCD is liquid nitrogen cooled andhas negligible dark current. You should only need one long dark frame per observingrun as a check on the dark current.

Flat Fields: images of a uniformly illuminated screen (also called dome flats). You needto do at least 10 (preferably more) for each filter that you used (B,V,R, etc.). If youremove the CCD from the telescope or reposition it or the filters, you will need to takean entirely new set of flat fields.

Sky Flats: also called illumination images or twilight flats. These are exposures of thetwilight sky. Your data images can also be included in this set, providing you have alarge number of frames with plenty of sky (i.e., your target objects are small). Youshould have about 10 illumination images in each filter. Again, if you remove the CCDfrom the telescope or reposition it, you will need to take an entirely new set of flatfields.

4.1. Procedural Overview

A short description of the image reduction process follows.

Overscan and Trim Correction: the overscan strip of the CCD is used to correct voltagedrifts in the readout amplifier. Once corrected, the image is trimmed to revmoe theoverscan region around the image as well as any bad edges.

Bias Correction: the pixel-to-pixel DC voltage level inherent in the chip is subtracted.

Flat Field Correction: the image is divided by a uniformly illuminated image to correctfor pixel-to-pixel variation in quantum efficiency.

Dark Correction: the dark current is subtracted from the image.

Illumination Correction: the image is divided by a combination of sky images to correctfor wavelength dependent low frequency errors in the dome flats.

4.2. The CCDRED Package

To load the CCDRED package, start up IRAF (by typing cl), type imred to load the imagereduction package then ccdred. The procedures you will use within the CCDRED packageare:

• ccdproc - the workhorse of CCDRED. This is the basic process that can be used torun all the important reduction tasks.

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• imcombine - this process will combine multiple calibration images into a single image.

• darkcombine - a variation of imcombine for dark frames - weighs dark frames by theirexposure time.

• ccdlist - will list images in the current directory, allowing the user to quickly determinewhat images he has and in what state of processing they are.

• mkskycor - will combine sky images into a super-sky-flat and smooth it.

• setinstrument - will allow the user to list the filters used in the data set. This isespecially useful when used with ccdlist.

It’s probably wise to start off with all CCDPROC’s options turned off. Edit the CCDPROCparameters (used eparam to start, :qw when done) until they read:

images = List of CCD images to correct

(ccdtype= ) CCD image type to correct

(maxcac= 0) Maximum image caching memory (in Mbytes)

(noproc = no) List processing steps only?

(fixpix = no) Fix bad CCD lines and columns?

(oversca= no) Apply overscan strip correction?

(trim = no) Trim the image?

(zerocor= no) Apply zero level correction?

(darkcor= no) Apply dark count correction?

(flatcor= no) Apply flat field correction?

(illumco= no) Apply illumination correction?

(fringec= no) Apply fringe correction?

(readcor= no) Convert zero level image to readout correction?

(scancor= no) Convert flat field image to scan correction?

(readaxi= line) Read out axis (column|line)

(fixfile= ) File describing the bad lines and columns

(biassec= ) Overscan strip image section

(trimsec= ) Trim data section

(zero = ) Zero level calibration image

(dark = ) Dark count calibration image

(flat = ) Flat field images

(illum = ) Illumination correction images

(fringe = ) Fringe correction images

(minrepl= 1.) Minimum flat field value

(scantyp= shortscan) Scan type (shortscan|longscan)

(nscan = 1) Number of short scan lines

(interac= no) Fit overscan interactively?

(functio= chebyshev) Fitting function

(order = 5) Number of polynomial terms or spline pieces

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(sample = *) Sample points to fit(naverag= 1) Number of sample points to combine(niterat= 15) Number of rejection iterations(lowrej= 3.) Low sigma rejection factor(highre= 3.) High sigma rejection factor(grow = 1.) Rejection growing radius(mode = ql)

4.3. CCDLIST—What do I got?

Normally, if you want to know details of an image, you use the IRAF command IMHEAD.IMHEAD will reveal exposure time, filter number, and the processing state of an image. Forexample, typing imhead ccd6034 gives the following output.

ccd6034[2043,2047][real]: Sa184-9

No bad pixels, no histogram, min=unknown, max=unknownLine storage mode, physdim [2048,2047], length of user area 1013 s.u.Created Wed 23:19:46 25-Jun-97, Last modified Wed 23:19:46 25-Jun-97Pixel file "HDR\$pixels/ccd6034.pix" [ok]New copy of ccd6034.imhNew copy of ccd6034.imhCHIP = ’TEK5’ / DETECTOR NAMETEL = ’LCO-40’ / TELESCOPE NAMEUTSTART = ’03 44 00’ / UT OF START FROM PCUTEND = ’03 54 03’ / UT OF END FROM PCFILTERP = 4 / FILTER POSITIONFILTER = ’4’ / FILTER NAMECCDPICNO= 6034 / FRAME NUMBER OF IMAGEEXPTIME = 600 / ACTUAL INTEGRATION TIME (S)GAIN = 2 / GAIN NOT NEC. E/DNLOOP = 1 / LOOP SIZELOOPCTR = 1 / LOOP COUNTERDATE-OBS= ’13Jul96’ / LOCAL DATE OF OBSERVATIONRA = ’000000.0’ / RA OBS-ENTEREDDEC = ’000000’ / DEC OBS-ENTEREDIMTYPE = ’object’ / IMAGE TYPETRIM = ’Jun 24 18:24 Trim data section is [1:2043,1:2047]’OVERSCAN= ’Jun 24 18:24 Overscan section is [2050:2064,1:2048] with mean=696ZEROCOR = ’Jun 24 18:24 Zero level correction image is /gonzo/starcounts/c40FLATCOR = ’Jun 24 18:24 Flat field image is /gonzo/starcounts/c40jul96/dflatCCDSEC = ’[1:2043,1:2047]’CCDMEAN = 1567.705CCDMEANT= 551748001CCDPROC = ’Jun 25 23:20 CCD processing done’ILLUMCOR= ’Jun 25 23:19 Illumination image is /home/didjeridu/gonzo/starcounITIME = 602.087

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Note the sections marked OVERSCAN, ZEROCOR, etc. These detail the processing historyof the image. The image listed above has had corrections for trim, overscan, bias, flat fieldand illumination applied. Flipping through a few dozen image headers can get tiresomethough, so the process CCDLIST will produce a list of the images in the current directoryalong with their processing history. You can then type ccdlist ccd*,

ccd6031.imh[2043,2047][real][none][B][OTZFI]:Sa184-9

ccd6032.imh[2043,2047][real][none][V][OTZFI]:Sa184-9

ccd6033.imh[2043,2047][real][none][R][OTZFI]:Sa184-9

ccd6034.imh[2043,2047][real][none][I][OTZFI]:Sa184-9

which lists the image name (ccd6031), the size of the image (trimmed to 2043x2047), thepixel status (real), the image type (none), the filter (BVRI, set by a translation file), theprocessing history (OZTFI) and the image name (SA184-9). The processing history lettersstand for:

• O = overscan correction applied

• T = trim correction applied

• Z = bias (zero) correction applied

• D = dark correction applied

• F = flat field correction applied

• I = illumination correction applied

The pixel status and image size are read by CCDLIST. Be aware that IRAF automaticallyconverts images to real (floating point) status when running CCDRED processes, which candouble the amount of disk space they take up. The image type, filter, and name must be setin the image header.

4.4. Test Images

You don’t want to apply any image correction without checking its affects on your images.I usually will copy several CCD frames of various types (a bias, a flat, a few images) intotest images (test1, test2, etc.). When I think I have a correction working properly, I applyit to the test images and make sure the results look nice (the eye is very good at this sort ofthing) before applying the correction to the entire data set. Go through your data set andselect out several images and use the IMCOPY command to copy them into test images.

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4.5. The Log File

It is generally wise to turn on the logfile option in the CCRED processes. The log file willrecord all the reduction steps you take. This can be very valuable later for reconstructingthe reduction when you realize that you screwed up.

To use the logfile, set the logfile parameter in any procedure you use to the name of the fileyou want. Generally, we use the unimaginative title logfile.

4.6. Trimming the Image and Correcting the Overscan

Not all images require trimming and overscan correction. In our department, only the FanMountain CCD has an overscan. Users of the ST-8 and other CCD’s can skip this section.

The Fan Mountain SiTE chip reads out a strip of constant signal (16 to 32 pixels) after eachCCD line. Theoretically, this should produce a broad line of constant flux on one edge ofyour chip. In practice, changes in the voltage of the CCD readout amplifier will cause thesignal to vary slightly. Overscan correction fits a function to this strip and thus corrects forvoltage variations.

When you trim an image, you cut out the sections that are not useful. The overscan sectionis not useful once you’ve applied the correction, so you can deep-six it. Sometimes, the firstor last line in a CCD images will also be useless. It is usually best to do trimming andoverscan correction at the same time.

The first thing to do is to use IMPLOT to determine which regions of the chip correspondto the overscan and which regions need to be trimmed out. It is probably wisest to do thiswith flat field frame.

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The command implot ccd6034 will bring up a plot of the middle line of your CCD chip ina separate window. You probably want to average over a few lines, so type “a:50” in thegraphics window to average over 50 lines. Now this plot (Figure 1) will show variations inbrightness across these lines. If you used an image frame, you will see large bumps fromstars. At the edge of the chip, the signal will fall off dramatically. You will see a spike atthe end of the image section and then a drop to a constant level. This constant level is theoverscan strip. The spike is garbage.

Position the cursor over the edge of the image and hit “e” to expand the view. You want toget a very accurate estimate as to where the overscan region begins. On the image in thefigure, the overscan strip is from column 2050 to 2080. Columns 2046 to 2049 are probablygarbage and should be cut. You also want to check the other end of the line to make sureyou don’t need to cut out low-numbered columns. In this image, they’re fine.

You also want to check in the y direction (column) to make sure you don’t need to trim outa few lines. In this image (Figure 2) the y direction is fine. Be aware of what the limits ofyour chip are. If your chip is 1054 × 512 for example, the signal will go to zero after 512.And remember that not all chips have an overscan region.

Open CCDPROC. IRAF uses a notation of [x1:x2,y1:y2]. There are four parameters youneed to change. Set overscan and trim to yes. Set trimsec to the area of the image you wishto keep. This is a backwards way of trimming, but it’s the way IRAF is wired. Set biassecto the overscan strip region. In my image, the overscan is over the entire range of y andfrom 2050 to 2080 in x. Note that it is generally a good idea to avoid the very edge of theimage, as well as near column 2048 where the amplifier is ramping down. I want to trim outeverything past line 2046. You will also need to fit the overscan region, so change interactiveto yes. So my parameters will be:

(oversca= yes) Apply overscan strip correction?(trim = yes) Trim the image?(biassec= [2050:2080,1:2048]) Overscan strip image section(trimsec= [1:2046,1:2048]) Trim data section(interac= yes) Fit overscan interactively?

Now run CCDPROC on your test images. The only one on which the overscan correction willshow is the bias image. Display the unprocessed bias image in one window of XIMTOOL.Then run CCDPROC on its test copy.

Typing ccdproc test1 will begin the processing of your image. Since you have set theoverscan fitting to interactive, you will be presented with a screen (Figure 3). This will showthe variations in the overscan region. They are usually very chaotic but there is an overalltrend in the data. It is this broad trend you wish to pluck from the overscan. In these firstfew images, you will actively fit the overscan. Once you have decided on a function, you willapply it non-interactively to future frames.

Within the overscan noise, you should see a solid curve. This curve represents the presentlyfit function. Use f to refit and plot the function until you do see it.

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The process of fitting an overscan region is quite complex. You can change the function(spline3 functions do well in general), the order, or the rejection parameters with a coloncommand (e.g., :order 2 would change the function to second order), then type f to applythe change. Each overscan is unique but there are a few ideas that you should stick to:

• You want to fit the broad trend in overscan. If your function follows every little wigglein the data, it is probably of too high an order and, if used, will create stripes in yourimages.

• Be aware of the scale. If the overscan is only changing by half an ADU, then a simple2nd order fit may do the trick well. On the other hand, oscillations of several ADU’sshould be fit, if they are broad.

• Don’t get too fancy. A 15th order function is way too complex. Generally, you want5th order or less. Only resort to higher orders if there is a gross structure that youmust remove.

• Sometimes a star landing on or near columns at the edge of the overscan will leakcharge into the overscan stripe, creating a spike. It is best to delete (with the d key)the offending points from the graph and interpolate over the region. Bias frames orflat fields will not suffer from this problem.

Once you are done fitting the overscan, the image will be trimmed. Display the test imagein the second window on XIMTOOL. You should see changes: (1) the image will be smaller,with the edges trimmed off, (2) broad horizontal bands of brightness across the image shouldbe smoothed out. If the brightness bands are not taken care of or new ones appear, you needto try again by recopying the original image onto the test image and CCDPROCing again.Again, be aware of the scale. A brightness fluctuation of half an ADU is no big deal.

Once you have decided on good overscan parameters and a good trim section, turn theinteractive mode off and run CCDPROC on your bias images. You could now apply it toevery image in your data set, but that might double the size of every image—a big problemif your computer disks are cramped.

4.7. Bias Combining and Subtracting

CCD images have a bias in them—a reflection of the DC bias voltage applied to the pixels.You need to subtract this out. The overscan correction will subtract out the bulk of it forthe Fan Mountain CCD, but one more step is needed.

Important Note: If your data was taken over several nights, you will need to process eachnight’s bias separately. For example, if you observed on two nights, you should have takena set of bias frames each night. When you combine them, you should combine the biasesfrom night one into one bias image (call it “Night1Bias”) and the biases from night two intoanother (“Night2Bias”). Keep this in mind while reading the rest of this section.

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In this section, you will learn to combine images. The bias level on any chip is, by its verynature, noisy. You can improve your image of the bias (and thus, your data) by averagingtogether a number of bias frames.

The IRAF procedure IMCOMBINE is the do-all software for image combining. The defaultparameters of IMCOMBINE are listed below:

input = List of images to combineoutput = List of output images(plfile = ) List of output pixel list files (optional)(sigma = ) List of sigma images (optional)(logfile= logfile) Log file(combine= average) Type of combine operation(reject = none) Type of rejection(project= no) Project highest dimension of input images?(outtype= real) Output image pixel datatype(offsets= none) Input image offsets(masktyp= none) Mask type(maskval= 0.) Mask value(blank = 0.) Value if there are no pixels(scale = none) Image scaling(zero = none) Image zero point offset(weight = none) Image weights(statsec= ) Image section for computing statistics(expname= ) Image header exposure time keyword(lthresh= INDEF) Lower threshold(hthresh= INDEF) Upper threshold(nlow = 1) minmax: Number of low pixels to reject(nhigh = 1) minmax: Number of high pixels to reject(nkeep = 1) Minimum to keep (pos) or maximum to reject (neg)(mclip = yes) Use median in sigma clipping algorithms?(lsigma = 3.) Lower sigma clipping factor(hsigma = 3.) Upper sigma clipping factor(rdnoise= ) ccdclip: CCD readout noise (electrons)(gain = ) ccdclip: CCD gain (electrons/DN)(snoise = 0.) ccdclip: Sensitivity noise (fraction)(sigscal= 0.1) Tolerance for sigma clipping scaling corrections(pclip = -0.5) pclip: Percentile clipping parameter(grow = 0) Radius (pixels) for 1D neighbor rejection(mode = ql)

You will have to set the parameters rdnoise and gain from the statistics for the chip. Theseshould be available from the course instructor.

There are several ways to combine. What IRAF does is create an image in which each pixelis the average or median of the corresponding pixels in each input frame. The combineparameter defaults to average. This is probably acceptable.

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One of the more important aspects of combining is rejecting pixels. Occasionally, a pixel is

hot or is struck by a cosmic ray. You want to have IRAF reject pixels that are far removed

from the average. You can reject pixels many ways - sigclip, avsigclip. The best, generally, is

ccdclip, which uses the noise parameters of your CCD to decide what to reject. The default

values for ccdclip are usually acceptable.

You should inspect your frames visually to make sure that they are all basically the same.

You may also use the IRAF process imstat to get statistics on your frames. The average or

midpt of each frame should be about the same.

Once you’ve set your parameters and rejected any bad frames, it’s time to combine. Type

IMCOMBINE. IRAF will ask you what images you want to combine. You can either

manually list all the images (e.g., ccd101, ccd102, ccd103 . . . ) or you can create a list.

Creating a list is simple and is very helpful when your are combining a large number of

images. You simply create a text file that lists the images you want. You can even add

pathnames if you want to combine images from different directories. For example, I might

create the list Biaslist which would have the contents:

ccd101

ccd102

ccd103

ccd104

\ bias \ ccd105

\ bias \ ccd106

When IRAF asks you for the images to combine, you respond with @filename. In the example

above, I would respond with @Biaslist. IRAF will also ask you for the combined file name.

Keep it simple. Something like “Bias”.

Visually inspect your combined bias frame. It should resemble your other bias frames, only

with a much smoother surface. If you are unsatisfied, you can try tinkering with the rejection

parameters or switching the combine function to median.

Once you are happy with your bias frame, apply it your test, dark and flat field frames. Go

into CCDPROC and change zerocor to yes and set zero to your combined bias image (“Bias”

in this example). Leave the trim corrections and overscan set, if you used them. You always

want to be certain that your images have had all the necessary corrections applied.

Remember: If you observed over several nights, you need to match the right bias to the

right data. Images taken on the second night of observing should be bias subtracted with

the combined bias frame from that night (“Night2Bias”, using the example at the beginning

of this section).

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4.8. Dark Combining and Subtraction

Dark current is the data that the CCD receives from itself. The longer a CCD is exposed,the more electrons is accumulates, which are added to the image. Dark frames are becomingrarer and rarer. The Fan Mountain CCD is cooled so that it does not really need them.The ST-8 and other chips can and should have their dark current subtracted at the time ofobservation as their current is fairly high. However, should you need to process dark framesseparately, this will guide you through the process.

Essentially, you will do the same thing you did with the bias frames. There is one crucialdifference. The level of dark current in each frame is directly proportional to the exposuretime. Since you may have various exposure times, you should scale the dark frames by this.The process DARKCOMBINE does this automatically. DARKCOMBINE essentially runsIMCOMBINE in such a way as to create a combined dark. Be sure to change the rdnoise,gain, combine and reject parameters appropriately. Combine your dark images into a framecalled “Dark”.

Once you have the combined dark frame, run CCDPROC again, this time on your test andflat field frames. Set darkcor to yes and dark to the name of your combined dark frame.

4.9. Flat-Fielding

You may take flat fields on the 26-inch and 40-inch by illuminating the surface of the domeand pointing the telescope at it. The 8-inch and 10-inch Meades will never have a flatfield screen. If you are using these telescope, you may skip to the section on illuminationcorrection.

CCD chips do not respond uniformly to light. Some sections of the chip are more responsiveto light than others. This is called a “flat-field” effect as it is most easily exemplified byshowing that a uniformly illuminated surface will not appear to be so on the uncorrectedCCD frame. To correct for this, you take images of a flat surface (a white screen), combinethem, and then divide all your images by the combined flat. Note that the flat field isdifferent for each filter since pixel response is wavelength dependent. Thus, you should startout by dividing your flat field images into directories, one for B filter i mages, one for V,etc. This will help you keep them separate. After you have separated the images, visuallyinspect them to make sure they look alike. Exposure levels may vary from frame to frame.

Once again, you will use IMCOMBINE to add together the flat field frames in each filter.You should combine them into something easy to recognize, e.g., “Bflat” for the B filter flatfields. There is one twist. Your flat fields will not have the same level of exposure. Somerecommend scaling them by their exposure time, but I have found this to be ineffective asthe lighting level on the flat field screen can change. You should change the scale parameterin IMCOMBINE to median.

Flat fielding is the second trickiest part of image reduction. When you are finished, applythe flat field to a test image in that filter using CCDPROC, setting flatcor to yes and flat tothe name of your image. Display the test image and its unprocessed original in XIMTOOL.

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You should note a marked difference between them. The flat field correcton is the mostdramatic and most obvious correction to an image that can be applied. There may still bea degree of non-flatness about the field, which will be corrected by illumination correction.

Once you are satisfied with the flat field correction, apply it to your test images and all ofyour data of that filter with CCDPROC. Then go onto the next filter and the next until allyour data is flat-fielded.

4.10. Illumination Correction

We are now at the last and trickiest part of image reduction—illumination correction. Wedo illumination correction for two reasons. First, sometimes a flat field is not available. Theonly flat field that can be found is the sky itself. Second, the flat field is not always evenlyilluminated by the flat field lamps. Flat field lamps are not the same color as the night sky -and the residual color affects the image at low frequencies. Illumination correction removesthese effects as both depend on one basic fact - the only uniform, evenly illuminated surfaceis the sky. Of course, the sky usually has stars and galaxies in it. We’ll have to get rid ofthem.

The simplest way to produce an illumination flat is to use imcombine to add all your imagestogether in each filter. Thus, stars and galaxies will be rejected when you average the CCDframes.

At this point, every image you have should have all the corrections except for illuminationapplied to them. You now want to go through your entire data set, image by image. Youwant to make a list, one for each filter, of the images that are “good” for illuminationcorrection. Bad images are those which have extremely bright (and large) stars within themor images with short exposure times. Generally, you want the sky level to be fairly high.Twilight flats are almost always acceptable.

Now, you should put the name of each image in a list file, as I suggested with the bias frames.The list should be selective by filter. For example, the list of good sky images in B filtermight be called Billumlist and might have the contents:

ccd1050

ccd1060

\ f40 \ ccd1062

\ f40 \ ccd1064

Now you will run IMCOMBINE on this image list (giving IRAF the name @Billumlist) whenit asks for the combine list). The parameters you used for flat-fielding should be acceptable.The output name should be something like Brough, as this is a rough sky flat, not onesmoothed by the process detailed below.

Once this image is produced, inspect it. It should produce a nice smooth image that willcorrect the residual flat-field on your images. Sometimes, I will simply use this image as my

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illumination correction (all you need do is used HEDIT to add the keyword MKSKYCORto its header). However, it is usually wise to smooth the image with MKSKYCOR.

If your combined sky flat shows bright blobs in it, you probably need to go back and eliminatean image with a bright star in it. Sometimes, you may have to mask out the stars in animage to get a good combined image. I will not detail the masking process here.

MKSKYCOR is an IRAF procedure that will take a combined sky frame and apply a boxcarsmoothing technique. It is very important that you eliminate any bad columns at this pointas they will cause problems with smoothing. The process FIXPIX or IMREPLACE willachieve this. I will not detail the process here.

The default parameters of MKYSKYCOR are generally poor for large chips. Change themto read:

input = Brough Input CCD images

output = Bsmooth Output images (same as input if none given)

(ccdtype= ) CCD image type to select

(xboxmin= 3.) Minimum smoothing box size in x at edges

(xboxmax= 0.05) Maximum smoothing box size in x

(yboxmin= 3.) Minimum moothing box size in y at edges

(yboxmax= 0.05) Maximum moothing box size in y

(clip = yes) Clip input pixels?

(lowsigm= 2.5) Low clipping sigma

(highsig= 2.5) High clipping sigma

(ccdproc= ) CCD processing parameters

(mode = ql)

Now run MKSYCOR on your unsmoothed image Brough and produce a smooth imageBsmooth. Inspect it. Your image should be a nice clear pattern. If you find small brightor dark rectangles, that is the result of bad pixels contaminating the sample. You need toeliminate them.

Once you’ve finalized an illumination image, apply it to your test images in that filter bysetting illumcor to yes and illum to your image name. Your images should now be smoothwith little variation in the sky across the chip. Once you are satisfied, apply the correctionto all the data in that filter.

Now you’ve got a reduced data set. Your next tasks will be to calibrate and analyze yourimages. Always make sure that photometric standard star frames are reduced identically tothings you want to calibrate.

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