How do Catadioptric telescopes achieve a much shorter, more portable tube length than refractors or reflectors of the same focal length?

Answer

By folding the light path many times using both lenses and mirrors.

Catadioptric telescopes, which include designs like the Schmidt-Cassegrain (SCT) and Maksutov-Cassegrain (MCT), function as compact optical systems by employing a sophisticated light path manipulation technique. These instruments utilize a lens element at the front, known as a corrector plate, in conjunction with primary and secondary mirrors. This arrangement forces the light to bounce back and forth multiple times within the tube before exiting to the eyepiece. This repeated folding of the light path allows the telescope to attain a very long effective focal length while maintaining a physically short, compact, and highly portable tube length, differentiating them significantly from straight-through designs like standard refractors or reflectors.

How do Catadioptric telescopes achieve a much shorter, more portable tube length than refractors or reflectors of the same focal length?

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