from the GNU version of the Collaborative International Dictionary of English
- n. a reflecting telescope invented by Cassegrain, which differs from the Gregorian only in having the secondary speculum convex instead of concave, and placed nearer the large speculum. The Cassegrainian represents objects inverted; the Gregorian, in their natural position. The Melbourne telescope (see Illust. under Reflecting telescope, below) is a Cassegrainian telescope.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a reflecting telescope that has a paraboloidal primary mirror and a hyperboloidal secondary mirror; light is brought to a focus through an aperture in the center of the primary mirror
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