A pure cassegrain telescope uses a parabolic primary mirror, just like a Newtonian telescope, but instead of a flat diagonal mirror, the cassegrain has a hyperbolic convex mirror that reflects the light back through a hole in the primary mirror. Cassegrains typical have a very long focal length, which results in high magnification. Cassegrains are popular with some planetary observers.

These telescopes have a hole in the main mirror. After the light has struck the main mirror it hits a second mirror, towards the aperture. Then the light goes through the hole in the main mirror and then into the eyepiece. The Cassegrain set-up can be combined with a Schmidt lens to make a Schmidt-Cassegrain. See also Newtonian telescope.

In its classical form, a compound reflecting telescope employing a parabolic concave primary mirror and a small hyperbolic convex secondary mirror to form images. Variations of the Cassegrain design include the Maksutov-Cassegrain and the Schmidt-Cassegrain.

A wide-angle reflecting telescope with a concave mirror that receives light and focuses the image. A second mirror reflects the light through a gap in the primary mirror, allowing the eyepiece or camera to be mounted at the back end of the tube.

A reflecting telescope in which the secondary mirror is mounted in front of the telescope and reflects light back down the tube through a hole in the center of the primary mirror to the eyepiece.