a reflecting telescope designed by Cassegrain, which varies from Gregorian only in obtaining the additional speculum convex as opposed to concave, and placed nearer the big speculum. The Cassegrainian represents objects inverted; the Gregorian, in their all-natural position. The Melbourne telescope (see Illust. under Reflecting telescope, below) is a Cassegrainian telescope.
a reflecting telescope that has a paraboloidal main mirror and a hyperboloidal additional mirror; light is delivered to a focus through an aperture during the primary mirror