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.
an astronomical reflecting telescope in which incident light is reflected from a large concave paraboloid mirror onto a smaller convex hyperboloid mirror and then back through a hole in the concave mirror to form the image
[C19: named after N. Cassegrain, 17th-century French scientist who invented it]