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Jan/O4/2001 Introduction to Telescopes Lab Page IT -1

I INTRODUCTION

Here we shall first discuss how a telescope works, the various designs, abilities and limitations.Thus will be followed by a lab exercise to directly experience each of the features discussed.

Most introductory Astronomy texts cover only the very basic details about large telescopes,insufficient for discussing the parameters of a smaller lab telescope. Thus an effort was made tomake this chapter complete in all .practical details. Part of the goal was to provide enoughinformation so that an intelligent choice can be made in the purchase of your own telescope. Inorder to accentuate the major points, the finer details are written in italics.

A. OBJECTIVESThe main purpose of this lab is to provide tasks for the student to learn to use the telescope,

with little other advanced preparation. The objectives are:

1. Understand basic optics of telescope designs, advantages and disadvantages of each.

2. Be able to recognize types of scopes and various focus configurations.

3. Learn to sight objects in finderscope, and eyepiece. Be able to change eyepieces (withoutlosing the object).

4. Directly experience light gathering power; be able to estimate magnitudes of images.

5. Measure directly the angular magnification; be able to measure angular sizes of images.

B. STUDENT PREPARATIONThere will probably be a video tape introduction of 30 minutes which will cover the discussion

part of this lab activity..It would be helpful if you give the discussion a quick reading before coming to lab..A ruler might be useful, as well as protractor. Bring your starmaps and lab manual!.A red flashlight and clipboard will be useful (its hard to read in the dark!)..Dress for cold weather! However, D..Q. coffee or food (or smoking) allowed at

observations!

C. INSTRUCTOR PREPARA TION (Students can ignore this)This lab activity should be first as it is introduction to telescope, and all other activities will use

the telescope. There are several indoor alternatives to be used for poor weather. It is notnecessary to wait for clear weather. Ideally the lab should follow a lecture presentation of thesubject matter.

A video tape introduction is available from ITV (Instruction TV). Universitv of California Davis [30minutes). It demonstrates several optical properties, integrated with a tour of telescopes at the UckObservatory, followed by an overview of the lab activity (and helpful hints on sighting telescopes).Extra copies of data sheets are needed for the students, along with some star charts. Specificparameters of the lab telescopes will need to be provided in advance for students to calculate

telescope properties.

Lf @Jan2001 , W. Pezzaglia Winter 2001SCU Astrolab

INTRODUCTION TO TELESCOPES Astra 6, Se;:: 2Physics, CSUSFall 1989

Pr~tiC81 Astronomy@ 09/01/89 W. P8ZZ8J118DisK: 17/IT

Most of the objects Astronomers wIsh to study are very far away In space and tIme. So muchso, that they are quite faint and so small no retail can be seen with the naked eye. Telescopes areoptIcal instruments resIgned to magnify these objects to see finer detaIl, and to amplIfy the lIght sothat faint objects can be seen.

A. OPTICSOptics is the science of us1ng lenses and mirrors to man1pulate light. Two common optical

instruments are the telescope and microscope.

I. AnDu1ar Size To study an object, you usually ~t as close as possible. The reason is, thecloser the object is, the bl~r its im~ on the retina of the eye. The fine retalls ere spread overmore neural receptors increasing your ability to distinguish. The apparent size of the object iscalled "angular slze" , e.g. the engles of ISo end 300 in flgures Ie and 1 b respectively.

Image or!reti na twic:e83 big

Figure Distant ObjectSmall Image

a Figure 1 b [lose Object,Bigger Image

Figure 1 c Lens used to construct a close image of a distant object

The smallest retail the eye can see is about 2', i.e. 2 arcmin (1'= 1/60 degree), called thevisua1 .:uity (vorie5 with individuo15, anywhere from l' to 3'). Unfortunately, m05tastronomical objects are so far BWey that their apparent angular size is quite abit smaller. Forexample, the only p10net that appr~he5 this size is Venus ot inferior conjunction ( 1').

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