Maksutov-Cassegrain telescopes provide a spectacular viewing experience in a compact design, offering a superior contrast that makes them excellent telescopes for planetary and double star observing. Also known as Mak-Cass telescopes, these telescopes appear similar to Schmidt-Cassegrain telescopes, but they differ slightly in design and are typically available with smaller apertures between 3.5 and 7.1 inches.
Like SCTs, Maksutov-Cassegrain telescopes are reflecting telescopes with a catadioptric design that uses both lenses and mirrors to minimize aberrations. The design works as follows:
- Maksutov Corrector Lens: Also known as a meniscus corrector due to its shape, this corrector lens is placed at the front of the telescope to correct the spherical aberration caused by the spherical mirrors in the telescope. The Maksutov lens accomplishes this using a highly curved spherical shape. This lens, however, is very thick, meaning it takes longer for a Maksutov-Cassegrain telescope to thermally equalize to outside temperature, especially larger models.
- Concave Primary Mirror: The light that passes through the meniscus corrector lens at the front of the telescope passes through the scope and hits a concave primary mirror. From here, the light is reflected, focusing toward the front of the telescope. Usually, these concave primary mirrors have a focal length around three times their diameter. For example, a typical 7-inch Maksutov telescope would have a 7-inch concave mirror with a focal length of 21 inches.
- Convex Secondary Mirror: The concave primary mirror reflects toward the front of the telescope, where it hits a convex secondary mirror. Many commercial Mak-Casses create this secondary mirror by aluminizing a small spot on the inside of the corrector lens. This mirror reflects the light back toward the primary mirror. However, the mirror serves a second function: it magnifies the focal length of the telescope. This allows the telescope to act much longer than it is. Usually, the convex mirror magnifies the focal length by a factor of five. If we follow the previous example, this means that a 7-inch telescope with a primary mirror of 7 inches has a focal length of 21 inches. The convex secondary mirror enhances this focal length by a factor of 5, resulting in an effective focal length of 105 inches, 15 times the diameter of the primary mirror.
- Eyepiece: The convex secondary mirror reflects light back through the telescope through a hole in the primary mirror, behind which lies the eyepiece. The light focuses there, where a viewer or camera can be placed for observation.
Like Schmidt-Cassegrain telescopes, Maksutov-Cassegrain telescopes are suitable for some applications, from terrestrial observing to astrophotography and stargazing. However, the differences in design between the two mean that Maksutov-Cassegrains function slightly differently than SCTs. While they have the advantage of not requiring periodic collimation of the optics, Maksutov-Cassegrains do have a longer focal ratio than other common telescope designs, meaning they require longer exposure times. This makes them less-suited for photographing faint objects in the deep sky.
Skies Unlimited offers quality Maksutov-Cassegrain telescopes for sale, as well as quality advice to help you choose the right model. Founded in 2004 by amateur astronomers striving to make astronomy more accessible, Skies Unlimited provides our customers with practical knowledge backed by years of personal and professional experience in the field. No matter what you need, from basic advice to advanced recommendations, we can help.
Whether you want to order a Celestron Maksutov, figure out how it differs from a Meade Maksutov, or ask how to get free shipping on your order, Skies Unlimited has an answer. Call Skies Unlimited today or visit our store outside of Pottstown, Pa., to speak with one of our team members.