LARGE TELESCOPE.

Ashburton Guardian, Volume 61, Issue 146, 2 April 1941, Page 6

LARGE TELESCOPE.

MIRROR UNDER SANDBAGS.

GRINDING WORK DELAYED

JOHANESBURG, Feb. 17

A mirror, to be fitted in the Southern Hemisphere’s largest telescope at the Radcliffe Observatory, Pretoria, is buried under sandbags “somewhere in England” as a precaution against damage by air raids. The story of how this came about is told in the South African Official Year Book.

In July, 1935, an order was placed by the Radcliffe Observatory with Sir Howard Grubb, Parsons and Company, of Newcastle-on-Tyne, for a 74in reflecting telescope. Considerable difficulty was experienced by the Corning Glass Company, of New York, in casting a disc of pyrex glass for the large mirror. This, however, was at last accomplished in August, 1938, when the disc was shipped to England for grinding and figuring. Unfortunately the mirror was not finished at the outbreak of the war and then the makers had to confine themselves to work for the fighting services. As a precaution, v the mirror has been buried under sandbags pending some other arrangement for its completion, possibly in America. The erection of the telescope itself was completed in 1938. It is housed in' a building 61ft in diameter and 65ft high, of which the upper portion is a cylindrical revolving turret. The telescope is driven electrically The frequency of the alternating current is controlled by a tuning fork and provision is made for sending the beam of light down the polar axis to a stationary spectrograph housed in a constant-temperature room. When the telescope is in operation on the southern stars, it is hoped that important contributions will be made to the knowledge of the structure of the stellar universe.