Gregorian telescope

Related Overviews

James Gregory (1638—1675) mathematician


More Like This

Show all results sharing this subject:

  • Astronomy and Astrophysics


Show Summary Details

Quick Reference

A reflecting telescope with a concave paraboloidal primary mirror and a concave ellipsoidal secondary mirror. The secondary mirror reflects light to a focus behind the primary, which must therefore have a hole in it. The advantage of the system compared with the Cassegrain is that the image is upright, but the drawback is that the Gregorian has a longer tube. Gregorians, proposed in 1663 by J. Gregory, were popular in the 18th century but are now rarely seen.

Subjects: Astronomy and Astrophysics.

Reference entries

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.