Question

What lens system is the Maksutov telescope an equivalent of? Write a paragraph

to explain the differences and similarities. Thanks a bunch!

Answer 1

Maksutov telescopes are another modification on Cassegrain optics.the principle of operation is similar to the Schmidt-Cassegrain telescope. They have a spherical primary mirror and a secondary mirror and have the same design. The difference to the Schmidt-Cassegrain with the Maksutov lies in its meniscus-shaped lens at the front aperture and no Schmidt plate. Maksutov-Cassegrain telescopes are an another design to the similar Schmidt-Cassegrain telescope (SCT). They are similar in most respects, there are few notabe differences between Maksutov-Cassegrains and SCTs.

The main difference between SCT and Maksutov-Cassegrains is the corrector lens at the front of the telescope. Both uses spherical mirrors that induces spherical aberration. The corrector lenses eliminate aberration, allowing them to be relatively inexpensive when compared to other all-reflective Cassegrain designs which includes expensive aspherical mirrors. SCTs use a flat Schmidt corrector which has a slight aspheric curve.Maksutov-Cassegrains use a highly curved spherical lens meniscus corrector to achieve the same effect. The drawback to the Maksutov design is that the corrector is much thicker (usually around 10% of the aperture, compared to about 3% for a Schmidt corrector). This leads to a longer time to thermally equalize to outside temperature of a Maksutov, especially for large sizes greater than 6"

Maksutov-Cassegrains usually have longer focal ratios than SCTs, making them less well-suited for deep-sky photography.

Many commercial Mak-Casses create the secondary mirror by aluminizing a small spot on the inside of the Maksutov corrector lens. This is convenient and less expensive, it is not as ideal as a separate secondary mirror with a slightly different (but more optimized) curvature. For small sizes this is not much of a problem, and small Mak-Casses tend to perform very well. Some high-end Mak-Casses use optimized, aspherical secondary mirrors instead of aluminized spots, and these instruments are excellent performers. They are especially well suited to planetary observing and imaging, but they are often quite expensive.