Astronomical Telescopes

JSGT 1951 V35 T260-T269

A survey is made of the development of astronomy from observations made by Eratosthenes in 250 B.C. up to the discovery of the refracting telescope by Lippershey in 1609. The development of refracting telescopes is described, and reference is made to the invention of reflecting telescopes. The difficulty of figuring mirrors to an aspherical surface and its consequences on the development of the telescope is discussed. The factors leading to the eventual triumph of the reflecting telescope and the vital contribution which glass makes to the science of astronomy are described. Passing into modern times, the problem of the telescope mounting is briefly discussed, together with a more detailed description of the method by which the smooth sidereal motion is imparted to the polar axis of the Mount Stromlo 74-inch reflecting telescope. Finally, the latest development in telescopic optical systems due to Bernhard Schmidt is discussed and reference made to the proposals for the Isaac Newton telescope. This, the largest of its kind in the world, is to be installed at the new Greenwich Royal Observatory, Herstmonceux Castle.

G. M. Sissox