Cassegrain telescope

US: (kas′ə grān′)

WordReference Random House Unabridged Dictionary of American English © 2025

Cas′se•grain tel′escope  (kas′ə grān′), [Astron.]

a reflecting telescope in which the light, passing through a central opening in the primary mirror, is brought into focus a short distance behind it by a secondary mirror. Also called Cas•se•grain′i•an tel′escope  (kas′ə grā′nē ən). 
• named after north, northern. Cassegrain, 17th-century French scientist, its inventor 1805–15