The Big Eye

Good news, long delayed, came from the California Institute of Technology last week. The 200-inch mirror for the mighty telescope at Mt. Palomar was finally pronounced finished. Grinding and polishing began in 1938, was stopped in wartime, and resumed at the end of 1945. Now the big glass disc, yellowish blue and slightly murky like an old Pyrex dish, is a paraboloid perfect within two millionths of an inch.

Since last July the opticians, directed by tall, spindly Dr. John A. Anderson, have been making the final tests. They proved that the great mirror will allow the pinpoint image of a star to diffuse into a spot whose diameter is equivalent to less than .07 seconds of arc. Such accuracy is better than necessary, since the normal turbulence of the atmosphere causes seven times as much distortion.

In about a month, the disc will go by truck to Mt. Palomar, 130 miles away. There the glass will be covered with a thin film of shiny aluminum and set in the telescope. Some night in the spring or summer of 1948 it will stare up at the sky as man's farthest-seeing eye.

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