ABSTRACT
In the modern sense, observatories are of course associated with telescopes of some kind or another. Aircraft have been used; the Kuiper Airborne Observatory, brought into use in 1975, was a Lockheed C141 Starliner jet transport aircraft, in which was mounted an 0.915 m Cassegrain telescope. Telescopes of both kinds were steadily improved, and really large instruments became possible; in 1789 William Herschel produced a reflector with a 49 inch mirror. The first multiple-mirror telescope was set up at the Whipple Observatory at Mount Hopkins, Arizona; it used six 183 cm mirrors in conjunction, so that the total light-grasp was equal to a single 442 cm mirror. The Hubble Space Telescope was launched from the Space Shuttle on 25 April 1990. A planetarium is purely an educational device; an artificial sky is projected onto the inside of a large dome, by means of a very complex projector.
