Catadioptric Telescopes
Catadioptric Telescopes - Schmidt-Cassegrain & Maksutov-Cassegrain
These telescopes might be thought of as a combination of reflector and refractor principles. They are closed tubes which combine relatively large apertures with short tube lengths. This is achieved by folding the light path internally using mirrors. The short tube design makes them very portable so they are very popular with astronomers who travel to dark sky locations.
Developed originally by Sieur Guillaume Cassegrain a French sculptor back in the late 1600’s, the idea was improved upon by Bernard Schmidt, an Estonian Astronomer and Dmitry Maksutov who both worked on adding front corrector plates between 1930 and 1940.
The combination of refractor and reflector principles tends to give excellent results for deep sky viewing with little or no aberration or halo around stars. These scopes are often computer driven for easy setup and starfinding and are a popular choice for astro-photography. Their cost is typically more expensive than a reflector while less expensive than a refractor of similar aperture.
Both Schmidt-Cassegrain and Maksutov-Cassegrain designs are highly regarded by ’serious’ amateur astronomers. The Maksutov version has a smaller secondary mirror which tends to give a better contrast.