| Gregorian telescope |
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A type of reflecting telescope proposed by James Gregory in 1663. The primary mirror is a paraboloid with a central hole and the secondary is ellipsoidal. In practice, Gregory was unable to obtain mirrors figured accurately enough to construct his telescope before Newton made the first working reflector to a simpler design with a flat secondary. Subsequently, the Gregorian design was rendered obsolete by the Cassegrain telescope. See also: Newtonian telescope. |