A design of optical telescope, incorporating features of both the Schmidt camera and the Cassegrain reflector. The Schmidt-Cassegrain employs a spherical primary mirror and a corrector plate to compensate for spherical aberration, as in the Schmidt camera. However, the prime-focus plate holder is replaced by a small convex secondary mirror, which reflects the light back down the tube and through a hole in the primary mirror. The image can thus be viewed visually, or a camera can be mounted at the back of the main tube. The resulting telescope is very compact, so the design is particularly suitable for portable telescopes and amateur and educational use.