A Maksutov is a type of catadioptric telescope developed between 1929 and 1941 by Dmitri Maksutov. The Maksutov differs from other catadioptric and reflecting telescopes in that it uses spherical and not parabolic surfaces. Normally spherical surfaces suffer from spherical aberration which causes unclear images, but the aberrations of the spherical front meniscus lens are counteracted by the aberrations of the back spherical mirrors.
Maksutov telescopes come in Newtonian and Cassegrain configurations, the latter being the most common and most rugged. Since the surfaces are spherical, they are cheap to make as they are easy to grind. Further, in the Maksutov-Cassegrain, the secondary mirror is simply an aluminized spot on the meniscus corrector plate. This makes the Mak-Cas a very rugged optical system as it is difficult to cause the system to become mis-aligned.
The advantages of the Maksutov telescope are good contrast and lack of coma, making them excellent for both planetary and deep sky observing. In this sense they provide the best of both refracting telescopes and reflecting telescopes.
The Maksutov does have two disadvantages over other designs. First, in order to avoid some forms of aberration, the focal ratio has to be quite high, at least f11, making Maksutovs quite slow photographically. Second, as the aperture of a Maksutov increases, so does the thickness of the front meniscus lens. There is a point where it will take an unreasonable amount of time for the meniscus lens to cool down for observing as such Maksutov telescopes don't scale up well. This means that it is unusual to see commercially produced Maksutov telescopes with apertures over 7" to 8".
- ↑ Telescope Engineering, Dmitri Maksutov, http://www.telescopengineering.com/history/DmitriMaksutov.html