What is a catadioptric telescope?

A catadioptric telescope, also known as a compound telescope, is an optical system that uses a combination of lenses and curved mirrors to offer a wider field of view with a lower probability of error than earlier types of telescopes. Astronomers built the first catadioptric telescopes in the 1930s.

Beginning in the 1960s, catadioptric telescopes using the Schmidt-Cassegrain design became the most commonly used type of telescope. The telescope includes a design element known as a corrector that allows the mirrors to fix errors caused by the lenses and the lenses to fix errors caused my the mirrors. Additional types of catadioptric telescopes include the Maksutov–Cassegrain and Klevtsov–Cassegrain.