The 10 Best Cassegrain Telescopes

Editor's Notes

April 07, 2020:

Cassegrain telescopes are good all-purpose telescopes, which are commonly used for deep-sky viewing and astrophotography. The most popular optical designs of these telescopes are Schmidt-Cassegrains (SCT) and Maksutov-Cassegrains (MCT). As with all Cassegrains, both types combine a primary concave mirror with a secondary convex mirror, however on the former, which include the StarBright XLT and the NexStar 6SE, the corrector is a shallow, complex curve, whereas on the latter, which include the Orion StarMax and the StarNavigator NG 125, the corrector is convex on one side, and concave on the other. In both instances, the corrector’s function is to remove aberrations created by the reflective mirrors at different focal lengths.

Both of these designs have their advantages, and there are trade-offs to consider when buying a Cassegrain telescope. Due to their spherical nature, MCT optics can be polished to higher precision, whereas SCT corrector plates are strangely curved, and it’s hard to attain the same degree of smoothness as with an MCT. When using comparatively-sized telescopes, you are more likely to achieve better results when using an MCT.

With that said, SCT’s have proportionally shorter tubes, as compared to MCT’s, so you can fit a longer focal length into a smaller space. This, portability, coupled with their suitability for narrow-field viewing of planetary objects, makes them a good choice for those looking to practice astronomy or astrophotography in the field.