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January 2004

SKY DISK
A Blank Look


The back resembled a 20-ton waffle, but it was the front of the 200-inch (500-centimeter) Pyrex "mirror blank" that absorbed New York-based Corning Glass Works physicist George McCauley, at left, with associate J. C. Hostetter. Though his first attempt was flawed, McCauley's second try (right) was successful; he babied that disk through flood, ridicule, and a rare upstate New York earthquake. In March 1936 he moved it to California, where it was polished to concave perfection (an 11-year process) to reflect and focus light in the Palomar Observatory being built near San Diego. In 1948 engineers installed the disk at Palomar—the world's most powerful optical telescope until Hawaii's W. M. Keck Observatory opened in 1993. Today Palomar still gives astronomers a nightly star-studded show.      
 
—Margaret G. Zackowitz
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Photograph by Robert Yarnall Richie, Corning Glass Works Photo, Corning, New York



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