Star Points for September 2008 by Curtis Roelle
World's Greatest Refracting Telescopes

Numerous telescope designs have been engineered in the nearly 400 
years since its invention. Every few years a new one breaks the 
world record for size. Others are launched by rocket into earth 
orbit where they peer out, returning inspiring images from high 
above the atmosphere. 

The oldest type of telescope is the "refractor" and, in spite of 
advances in telescope and glass technology, the world's largest 
refractors have maintained their lofty status for well over a 
century. The refracting telescope has become the quintessential 
telescope, and many people, picturing a telescope in their mind, 
envision a refractor, whose distinctive profile features a lens at 
one end of a long tube and an eyepiece at the other.  

As part of the common culture, refractors have frequently been 
employed as movie props. Using the piggybacked Zeiss refractors at 
Los Angeles' Griffith Observatory, actress Lee Grant observed the 
sun in the psycho-horror thriller Mafu Cage.  Griffith also 
appeared in other movies from Rebel Without a Cause, starring James 
Dean, to the science fiction classic Terminator, with Arnold 
Schwarzenegger.

When it was completed in 1873 the 26" refractor built by Alvan 
Clark and Sons for the U.S. Naval Observatory in Washington was the 
world's largest.  (The size refers to the diameter of the main 
lens.) I've had the pleasure of observing with this historic 
instrument. Although it remains in use today, within a decade it 
was upstaged by an even larger refractor.

Then in 1888, the Clarks built a new, 36" refractor that became the 
world's largest.  It was placed in an observatory whose site was 
selected to optimize the capabilities of the instrument.  Lick 
Observatory is on Mt. Hamilton in California's Diablo Range 
overlooking the "Silicon Valley".  

I visited Lick in late August during a business trip to San Jose.  
The first glimpse I had of Lick was from the airplane window during 
its descent into San Francisco International Airport. After touring 
San Francisco I crossed the Bay Bridge into Oakland and headed 
south down Interstate 880. I had not driven very far when, while 
admiring the mountains on the horizon, I spotted Lick Observatory 
on a distant mountaintop.  The observatory was some 50 miles away, 
but in the clear dry air it seemed much closer.  

I recommend a visit to Lick for anyone traveling to the Bay Area.  
Lick has weekend evening public observing using the 36" itself. The 
cameras and other instruments have been removed. Only an eyepiece 
is used. Visitors use the telescope in the fashion it was 
originally intended: eyeball to eyepiece.
	
Lick's 36" remained the world's largest refractor for only nine 
years. In 1897 the Clarks built a 40" refractor for Yerkes 
Observatory in Wisconsin.  More than a century later these two 
remain the largest refractors in the world.

In a world of rapid changes, there are few things that stay the 
same.  The great Clark refractors, however, still operational and 
accessible to the public, are exquisite examples of timeless 
craftsmanship.