Maksutov

A lens instead of a correction plate? Maksutov telescopes are different, SC telescopes too. But their construction is similar. So what is the difference?

A Maksutov is a variation of a Cassegrain telescope. It works in the same way as a Schmidt-Cassegrain telescope. It has a spherical primary mirror and a secondary mirror. The structural form is the same. So what's different?

Lens instead of correction plate

The difference to the Schmidt-Cassegrain: the Maksutov has a meniscus-shaped lens on the lens aperture and no Schmidt plate. The Maksutov telescope is named after Dmitri Maksutov (1896 - 1964), a Russian optician and astronomer, who introduced this telescope design in 1941..

A telescope for planetary observing

But what are the benefits? With a uniform thickness of the lens, the system displays only slight chromatic aberration. In addition, it corrects the spherical aberration created by the primary mirror.

The system’s secondary mirror is vapour-deposited on the rear side of the meniscus lens. Therefore, there are no secondary mirror spider vanes which would bend the light. Since the secondary mirror is small, there is only a small amount of shadowing. This means: very good contrast, comparable to that of a refractor.

Are there any disadvantages?

Although this telescope has many advantages, there are of course also disadvantages, because no instrument is perfect in every way. But that’s not so important. What matters is that you find the right telescope for your observing requirements.

It takes a very long time to cool when the temperature changes, for example when you take the instrument outside.

The optics are relatively heavy, which is due to the lens. Just like a Schmidt-Cassegrain, the Maksutov has a small field of view, since it has a focal ratio of between 1:10 and 1:13. Fast systems are not possible with the prevalent instruments (Gregory style), as existing image defects would be amplified.