Volume 9, Issue 8

The Sunset Gaze t te Serving the Tri -Cit ies s ince 1975

Sunset Astronomical Society

Meeting information

Meetings are generally in the theater in the Delta College Planetarium in Bay City. The meetings will usually be on the 2nd Friday of each month at 7:00 PM. Watch the newslet-ter for changes in dates and times. Member-ship is not required to participate in meet-ings and activities. See last Page for this

month’s meeting site.

Membership Information

Our club has switched to e-mailing our newsletters. For those wishing to receive a hard copy mailed an additional dues of

$10.00 per year is required.

Student / Senior: (17 years & younger,

65+ years)

1 year - $15 (mailed Newsletter add $10)

2 year - $20 (mailed Newsletter add $10)

Regular: (18+ years)

1 year - $20 (mailed Newsletter add $10)

2 year - $30 (mailed Newsletter add $10)

Family:

1 year - $25 (mailed Newsletter add $10)

2 year - $40 (mailed Newsletter inclusive)

Membership includes voting privileges, the newsletter and free admission into Delta

College Planetarium shows.

Treasurer’s address for renewals and

subscriptions:

Tom Smith, 3423 Hidden Road,

Bay City, MI 48706-1243

Subscription Information

Subscription prices for “Sky and Telescope” Magazine or “Astronomy” Magazine are available at club rate with the purchase of individual or family membership. For prices please refer to the treasurer or the club’s

website:

http://www.sunsetastronomicalsociety.com/

SASMembership.htm

April, 2012

The Race for the largest Refractor on Earth -

A 19th

century Question of Honor

This is the third part of a new series about the ’arms’

race in the 19th

century to build the largest refractor

on Earth. Countries like the United States, France,

England, Germany, Russia, Austria (then the K. u. K.

monarchy), and finally Sweden all tried to outdo each

other with ever larger (and longer) refractors pushing

this telescope design to its technological limit only to

be surpassed at the end of 19th

century by the first

large reflectors.

In the last SAS newsletter we arrived in Berlin and saw

the construction of the largest German refractor: The

double telescope in Potsdam – but it is the not the

one with largest focal length or the longest tube

lenght. That honor goes to the “Big Gun” of the Ar-

chenhold Observatory in Treptow, Berlin, which has

an aperture of 68 cm (26.8 inch) and a focal length of

21 m (68.8 feet, F = 31). The 160 ton telescope does

not have a dome and was build by Steinheil and Hop-

per and is still in use for public outreach. The picture

on the right and below gives you an impression about

the size of telescope.

We cannot close our story with some late comers in

the 20th century.

In 1900 at the

world exhibition in

Paris something

special was to be

presented in the

honor of the

Grande Nation: A

refractor which

should surpass

any other. The

location in Paris

was not well

suited but the

shear size of the

telescope lead the

project to became

a literal mayfly

with no scientific

value.

PAGE 2 THE SUNSET GAZETTE VOLUME 9, I SSUE 7

The lens had an astonishing diameter of 125 cm (49.2 inch)

and weighed 1.8 tons. Even at Yerkes the deformation of the

lens under its own weight and the diminishing optical proper-

ties and performance was noted and so it was decided to build

the refractor as a horizontal telescope with the lens set up in

north-south direction. Given a focal length of 57 m (186.9

feet) there was not much choice anyway - albeit a tube on a

German mount of this size would have been a sight to see!

For sky observations a plan mirror (coelostat) with 2 m diame-

ter was placed in front of the telescope to direct the light into

the lens. Even the focuser (see picture below) was so big it

had to be moved on rails. Observations were very difficult and

not frequent. The minimum magnification was 500 times and

the field of view was only 3 arc minutes and the idea to pro-

ject the image onto a 400 m2 big screen was a failure. After

the exhibition the telescope did not find a buyer and was de-

mounted: The lens and the mirror came to the Observatory of

Paris and the Yerkes refractor again was the largest refractor of the

world.

Despite the fact that the reflector design by then had won the overall

competition there were some large refractors build in the 20th

century.

In the year 1912 the Observatory of Hamburg-Bergedorf received a 60

cm (23.6 inch) refractor from Steinheil. After extensive renovation the

instrument is now open for public access again. In 1914 the 76.2 cm (30

inch) Thaw refractor was set up at the Allegheny Observatory in Pitts-

burg. The instrument was build by John Brashear and has a 14.4 m (47.2

feet) focal length and serves the astrometry even today. In 1985 the

original lens was replaced with one that is corrected to bring the red

light to focus because the photo-multiplier tubes of the attached Multi-

channel Astrometric Photometer (MAP) were more sensitive to red

light. Fortunately the Pittsburgh skies are still fairly dark in this region of

the visual spectrum.

Left: The original Brashear lens to the 30 inch refractor telescope. The lens was replaced by another 30 inch

made by the University of

Arizona in 1985 that cur-

rently resides in the Thaw

refractor. Photo Al Paslow.

Right: The Allegheny Obser-

vatory — Pittsburgh, Pennsyl-

vania.

30-inch Thaw Refractor,

1988.

(Photo Credit: Allegheny Ob-

servatory)

The last big refractors were

put in service in 1972 at the

Hida Observatory in Japan (see photo on the next page)

and on top of the Llano del Hato in Venezuela. Both instru-

ments were made by Zeiss and have a 65 cm (25.6 inch)

lens with 10.5 m (34.4 feet) focal length.

At 3600 m above sea level the refractor in Venezuela also holds the record of

being the highest in the world.

Left: The Hida refractor was constructed in April 1972, and is still the largest

refractor telescope in East Asia. The telescope has two advantages that make

it ideal for studying planets

and/or the nuclei of comets: Its

long focal length and the stable

and clear observing conditions

at Hida observatory. The tele-

scope observes storms and

clouds on Mars, and seasonal

variations in its atmosphere.

A sad fate was in store for the

Grubb build Yale-Columbia tele-

scope (66 cm or 26 ‘’ lens di-

ameter; 10.6 m focal length): In

1925 it was put in service at the

University of Witwatersrand in

Johannesburg, where it was

used for stellar parallax work. In

1952 it was transported to the

Australian Mount Stromlo Ob-

servatory where it served a

similar research function, but in

recent years has been used by

local amateurs for serious re-

search programs. As you may

know in April 2003 a bush fire

destroyed this great instrument

along with 5 other instruments.

Right: A photograph of this telescope

appeared in the February 20 issue of

newspaper The Australian, titled

'before and after'.

In 1928 the Yerkes refractor nearly

lost its title as the world largest refractor. Russia had ordered a 41 inch instrument

from Grubb for a remote observatory on the Crim. The dome and the mount had

already been completed (by the successor Grubb-Parsons) but the two 105 cm

glass blanks were rejected because of flaws which led to the stop of the project.

In 2002 competition arose again this time from the Swedish Solar Telescope (SST)

on top of the 2400 m Roque de los Muchachos on the canary island La Palma.

With 107 cm (42.1 inch) diameter the lens is actually bigger, but the effective ap-

erture is 97 cm (38.2) - smaller than the Yerkes but still bigger than the Licks re-

fractor.

Realistically there can be no sign of a refractor revival with the exception of ever

more affordable apochromatic refractors for amateurs. The future clearly belongs

to the reflector like the 39 m Extremely Large Telescope which should go into ser-

vice at the end of this decade. Still, the remaining working refractors have lost

nothing of their fascination. 40 instruments have lens diameters larger than 50 cm

and seven larger than 70 cm and most visitors still marvel when they stand in front

of some of the most impressive relicts of this important epoch of astronomy.

PAGE 3 THE SUNSET GAZETTE VOLUME 9 , I SSUE 8

The Swedish 1-m Solar Telescope (SST) on the island

of La Palma, Spain.

Martin Grasmann Secretary - SAS 6108 Summerset Drive Midland, MI 48640

SUNSET ASTRONOMICAL SOCIETY THE SUNSET GAZETTE SERVING THE TRI- CITIES SINCE 1975

UPCOMING EVENTS Welcome members and guest

New and old business

Club Business

Vote on the ballot to combine the

SAS and AU clubs

Treasure report

Refreshments Break

Presentation:

TBD

If clear we will observe on the

observation deck.

Apr 2-3 Evening: Look to the west when Venus

passes through the southern outskirts of the

Pleiades. Best viewed with a binocular of a wide field

telescope. On the 2nd you can see the waxing gib-

bous Moon forming a shallow arc with Mars and

Regulus and on the 3rd forming a narrow triangle.

Apr 6: Look out for Spica close to the Moon’s left

and brighter Saturn farther left to Spica.

Apr 5: Full Moon.

Apr 15 All Night: Saturn is in opposition and can be

observed the whole night through.

Apr 13: Last Quarter Moon.

Apr 17 Evening: Venus shines to the left of a very

thin crescent Moon

Apr 21: New Moon.

Apr 21-22 Late Night: Watch out for the modest

Lyrid meteor shower which peaks tonight at new

Moon. Best views are from midnight to the first light

of dawn on the 22nd.

Apr 22 Dusk: An excellent photo opportunity arises

with Jupiter shining below an extremely thin crescent

Moon very low in the west-north-west twilight.

Apr 23 Early Evening: A very thin crescent Moon can

be found to the left of the Pleiades.

What’s up in the Sky SAS Meeting

Start: 7:00 PM

Friday, Apr 13th, 2011

Delta Planetarium

2012 SAS PROGRAM

April 13 2012 TBD

May 11 2012 Election and swap meet.

June 8 2012 ?

TBD spots are still open for presentations

Contact Timothy Ross, Phone (989)-777- 2824 or tjrastronomy@hotmail.com

Venus Transit June 6 2012: http://eclipse.gsfc.nasa.gov/OH/transit12.html

Annular Solar Eclipse 2012: http://eclipse.gsfc.nasa.gov/OH/OH2012.html

#SE2012May20A

This issue can be accessed in color on the website of the SAS!!!

http://sunsetastronomicalsociety.com

Elected Officers for the SAS: President, Tim Ross tjrastronomy@hotmail.com

1. Vice President, Debra VanTol debraj106@aol.com

2. Vice President, Mohammed Khan khan001@charter.net

Treasurer, Thomas Smith tom55net@att.net

Secretary, Newsletter Editor, Martin Grasmann martin.grasmann@sbcglobal.net

Apr 24 All Evening: Venus to the upper right of the

thin crescent Moon.

Apr 29: First Quarter Moon.

Apr 30 Evening: Watch out for bright Mars and

dimmer Regulus above the Moon.

May 6: Full Moon.

Vote on the proposal to unite SAS and AU clubs

Dear SAS Members,

By know you should have received the paper ballot for the vote via e-mail. Those who have no e-mail account or have not voted by regular mail can cast their vote on the April 13th SAS meeting.