Giant Optical Devices

Introduction There is currently great excitement and enthusiasm for building a giant telescope. In this paper we assess the alternatives and bring together some history and experience to help guide us to a successful telescope. We briefly review possible telescope configurations and then review the history of telescope building, with the goal of gaining insight into the appropriate size for the next generation telescope, and the time scale likely to be involved. We briefly review the major scaling laws for materials to provide some insight into the likely difficulties in building larger optical telescopes. Sensitivities for very large telescopes are given, as a succinct guide to the scientific potential of larger telescopes. We then review some factors that influence the design, cost and schedule of a telescope project. Since Adaptive Optics (AO) is likely to be a key ingredient in the next generation of telescopes, we also review the major scaling laws for AO, to indicate the difficulty of AO for giant telescopes. We end with a strawman design concept for a 25 m telescope, indicating some ideas that may make such a telescope much more cost effective than the 10 m segmented Keck Telescopes, the world’s largest telescopes.