Catadioptric telescopes use a combination of mirrors (reflection) and lenses (refraction) to create an image within your eyepiece (or camera). This process allows for less distortion and higher focal length in a compacted telescope. Their heavy weight and compact size make this telescope ideal for astrophotography, especially if you’re needing a very narrow field of view.
These telescope types employ various different image correction techniques to eliminate aberrations and image-warping within the field of view.
The most common types of catadioptric telescopes are:
These telescope types have a ‘flat’ front lens where the main corrections take place at the primary mirror with minor corrections continuing along the path to the apex.
These telescopes almost always have a visibly curved main ‘negative’ lens at the opening of the scope whereupon the path light is corrected upon entering the OTA with minor corrections continuing along the path to the apex.
For more technical or detailed information about any of these types of scopes, view any of the sites below for more information:
Wikipedia; Catadioptric System:
Wikipedia; Schmidt-Cassegrain Telescope:
Wikipedia; Muskatov-Cassegrain Telescope: https://en.wikipedia.org/wiki/Maksutov_telescope#Maksutov.E2.80.93Cassegrains
Starizona; Schmidt-Cassegrain Telescope:
Starizona; Muskatov-Cassegrain Telescope: