The Main Ideas : The Types Of Reflecting Telescopes

The Cassegrain telescope has a parabolic primary mirror and a hyperbolic secondary mirror that reflects the light through the hole in the primary mirror. This kind of telescope is designed to be small and and simple, and protects the parts inside the telescope. The image to the right shows how the Cassegrain telescope works. The Ritchey-Chrétien, Dall-Kirkham, and Schiefspiegler are all reflected telescopes based off of the Cassegrain.





The Gregorian Telescope has a concave secondary mirror instead of a convex. This type of telescope is useful for land observations, and it isn't very common anymore. The image on the left shows how the Gregorian Telescope works.


Nasmyth reflectors are similar to the Cassegrain reflectors. However, the Nasmyth telescopes don't have the extra hole in the primary mirror, but a third mirror that makes the light bounce off to the side.