A GIANT TELESCOPE

Auckland Star, Volume LXIX, Issue 192, 16 August 1938, Page 8

A GIANT TELESCOPE

After four years of grinding and polishing, the lens of the large telescope for the new Mac Donald Observatory, no* Hearing completion at Mount Locke, near Marfa, Texas, and weighing 56001b, will eoon be shipped. In the course of the four years, during which operations were carried on for only fifteen minutes a day, the disc, twelve inches thick and eighty-two inches in diameter, had ite top flat surface changed to a paraboloid with -a maximum depth in the centre of one and a half inches. This could have been accomplished in a very short time but for the fact that continuous operations would heat the glass and spoil the uniform internal structure. This would cause it to warp under temperature changes and distort the pictures of the stars.

The telescope into which the lene will fit will be the'second largest in the world, exceeded only by the 100-inch lens at Mount Wilson. The cylindrical structure, in the bottom of which the lens will be placed, and which can be turned in any direction on its equatorial mounting, weights forty-five tons, but is of such fine workmanship that it can : be moved by the touch of a finger. Its motions will be controlled by electric motors governed by extremely accurate clocks.