The Catadioptric telescope uses a combination of two systems. The Catadioptric telescope forms an image with the use of a mirror (catoptric system) and lens (dioptric system).
a short optical tube,
a primary mirror,
a secondary mirror and
a glass corrector.
The path of light in Catadioptric telescopes (Available from https://sites.google.com/site/mrwilkinsonphysics/classes/s4-physics/optical-telescopes. [accessed 29 Oct 2019] )
The optical tube in the Catadioptric telescope is sealed and quite small in size. The light enters the optical tube and passes through the glass corrector, installed at the front of the optical tube of the catadioptric telescope.
The primary function of the glass corrector is to limit the spherical aberration. Light rays travel to the primary mirror at the bottom of the catadioptric telescope.
The beams are collected and bounced towards the secondary mirror. From here, the light reflects through a hole in the primary mirror to an eyepiece.
With the right position of mirrors and lens, the light is "optically folded," meaning that the effective focal length of the telescope increases while the mass reduces – which makes catadioptric - telescopes easier to produce.
Two of the most popular designs of Catadioptric telescope are:
Both catadioptric telescopes are very popular and have a pretty similar design, but there are some differences.
Schmidt-Cassegrain telescope and Maksutov-Cassegrain differ in:
corrector plate and
Maksutov-Cassegrain telescope uses a thicker corrector lens and a different secondary mirror that is located inside of the corrector lens. Telescopes also have different aperture sizes – The schmidt-Cassegrain telescope is designed to have a bigger aperture than Maksutov-Cassegrain telescope.
Catadioptric telescopes have shorter optical tubes than refractor telescopes and reflector telescopes. This means that they take up less space and are easier to move. Their secondary mirror degrades the performance for planetary and Moon observations, but overall they are still great telescopes for observing all celestial objects.
A short presentation of the Catadioptric telescope is available here.