A BIG TELESCOPE

Ashburton Guardian, Volume 53, Issue 15, 28 October 1932, Page 8

A BIG TELESCOPE

SECOND LARGEST IN WORLD. NEW CANADIAN OBSERVATORY. There will be.- completed next year at Newcastle-on-Tyne, England, the second largest telescope in the world. It will bo shipped to Canada and erected in a new observatory located on high ground a few miles north of Toronto. The observatory is being built as a memorial to the late Mr David A. Dunlap, who in his lifetime was a keen student of astronomy, funds being provided by his widow and son. Upon completion the telescope will be presented to the University of Toronto and will be conducted by the Department of Astronomy of that institution. The buildings comprising the observatory will stand in the midst of a 177-acre'plot of land, 800 ft. above sea level, and the property will be beautified by the Faculty of Forestry of the University and will be known as the David Dunlap Park. The main telescope is of the reflecting type. In place of a lens it will be equipped with a concave mirror to collect light rays from a star and. bring them to _ focus. This mirror wilbhave a clear aperture of 74 inches, and will be fashioned from a disc of glass 12 inches thick and weighing about two and a half tons. The order for the telescope was placed two years ago, and its construction is well advanced although it will not be completed until next summer.

Special machinery was built to fashion the huge bearings of the apparatus and to polish the glass. The casting of the immense block of glass, the annealing and the grinding and polishing of its surface to a correctness of one-half millionth of an inch, is a lengthy process, but every effort is being made to have the apparatus in working order by December, 1933. The structure which will contain the huge telescope will be a circular building, 61 feet in diameter,, surmounted by a metal hemispherical dome, which will be revolved by an electrical motor. The framework is of steel. The walls will be 2 feet thick, and hollow, being sheathed on the inside and outside with galvanised iron in order that temperature changes will not affect the delicate mechanism of the telescope. The inner and outer surfaces of the dome, also two feet apart, will be covered with a special mixture of papiermache. The outer surface will be covered by a layer of sheet copper for protection against the weather.