Cassegrain

/ˈkæsɪɡreɪn/ noun

Definition

A type of telescope design with a curved primary mirror and a smaller secondary mirror that reflects light back through a hole in the primary mirror.

Etymology

Named after Laurent Cassegrain, a French priest and optician who described this telescope design around 1672. The instrument bears his name as credit for the optical innovation.

Kelly Says

Cassegrain invented his telescope design specifically to avoid the awkward positioning of Newtonian telescopes—by bouncing light back through the main mirror, astronomers could observe from behind the telescope instead of awkwardly at the side, making it practical for larger instruments.

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