Science: Exacting Mirror

The world’s most troublesome piece of glass, the 200-in. mirror of Palomar’s Hale telescope, is back in shape again. Observatory Director Dr. Ira S. Bowen announced last week that the mirror, which was taken out for repolishing last May, has been tested on the stars and pronounced O.K. In places as much as 20 millionths of an inch of glass was polished off. Next step will be to cover the mirror with its shining coat of aluminum. Dr. Bowen hopes the big telescope will be hunting nebulae again by the first of the year.