noun
Cassegrain telescope
A type of reflecting telescope that uses a concave primary mirror and a convex secondary mirror to fold the optical path, resulting in a compact tube.
カセグレン望遠鏡は、鏡筒が短いので持ち運びに便利だ。
A Cassegrain telescope is portable because its tube is short.
Named after the French priest and physicist Laurent Cassegrain, who proposed the design in 1672.