The Orion 7” Maksuov-Cassegrain is a telescope manufactured and sold by Orion telescopes in the USA. It is not very commonly known amongst dedicated astronomers, but it may be interesting for a few looking for a specific purpose telescope. It is based on the unusual Maksutov-Cassegrain telescope design typically only seen in smaller telescopes due to the difficulty of manufacturing. The Orion 7” Mak is one of the largest commercial maksutov telescopes out there, but what advantage does the optical design give you? That is what I will be discussing today.
How does a Mak-Cass work?
The Maksutov-Cassegrain telescope (we’ll use Mak for short) is a type of hybrid telescope that integrates both mirrors and lenses into its optical design. A commonly seen example of this type of telescope is the Schmidt-Cassegrain by companies like Celestron, or SCTs for short. The optical design of both SCTs and Maks are quite similar, in the way that they use 1) a glass corrector lens at the front of the scope, 2) a fast primary mirror at the back of the scope, typically around f/2, and finally 3) a convex secondary mirror back at the corrector plate.
The Mak design allows for the corrector plate to be much thicker than an SCT for example, which unfortunately can be a major disadvantage, as it means that there is much more glass to cool down. The secondary mirror is just a coated section of the corrector plate (sometimes with differences in corrector figure), which means that collimation of the secondary mirror is unnecessary. This is an advantage over SCT’s, as on Maks there is no collimation required at all.
The specifications of a Mak telescope also require the tube to be a fair bit longer than say an SCT, which means that the scope is a fair amount heavier. This allows for a longer focal length though, which can be very beneficial for planets. The focuser on any Cassegrain typically moves the primary mirror, which is also the case with this telescope. The eyepiece is then inserted at the back of the telescope.
The Orion 180mm Mak, as mentioned before is a Mak-Cass style telescope. This comes with some unique specifications compared to say a typical refractor or reflector telescope. In this portion of the review, I will discuss the technical specs of the telescope, and what they mean for you.
- The aperture is 7 inches or 180mm. This is a decent size for the amount of light you are getting but is nothing extravagant or tiny, however as said before, for Maksutov telescopes, 7” is quite a large aperture.
- The focal length of this telescope is 2700mm, thus making the focal ratio (FL / Aperture) F/15. This is the main feature that makes the 7” Mak different from the competition, especially the F/5 and faster scopes astronomers have become accustomed to. Typical F/5 7 inch scopes would be about 1000mm long and have a focal length of 1000mm. Compare this to the Mak, which has a 2700mm focal length! The focal length determines how wide a field of view you can achieve (which is also dependant on camera sensor size, but we’ll assume that we use an identical camera.). A wide field of view allows you to capture larger objects in the sky, such as nebulae or constellations rather than being limited to smaller nebulae and galaxies with longer F/ratio telescopes. A smaller field of view, like the one you will get with the Mak, can be useful for targeting smaller deep-sky objects, or ideally lunar and planetary targets.
- The Mak has an extremely small body, similar to that of an SCT Telescope. This means that you will be able to move the telescope around without much strain as the length of the telescope is not much of an issue. It also weighs only 6.8 kg or 15 lbs, making it quite light for its aperture, which makes it easy on you and your telescope mount.
Only one real use, only 1.25 eps
The Orion Mak-Cass is not a very well known scope, and that is not for no reason. Many people have very little need for a telescope that has such a long focal length. This scope has quite a few disadvantages which I will talk about in this section.
- The telescope, as discussed before has a focal length of 2700mm. This is quite long for any telescope, and unfortunately what that means for astronomers is that it is extremely limiting in terms of what you can do with the telescope. The long focal length is favorable for planets, and you can certainly get some great planetary images. Unfortunately, what that means is that you will be limited very much if you want to perform deep-sky astrophotography or visual observing, as the field of view is extremely constricting.
- The aperture of the telescope does not turn any heads either. While this is a relatively large 7” Mak telescope, this is very small for deep-sky observers and is in most planetary observer’s eyes a small scope. This means that you will not get very much planetary detail, and even a relatively cheap 8” Dobsonian telescope would most likely beat the Mak in not only deep sky, but planetary observing.
- Because of the f/15 focal ratio, this means that any views, whether they be planetary or deep-sky will be very dim.
- The telescope is lacking in terms of accessories, especially at the cost Orion sells it for. For example, if you plan on doing any visual observing with this scope, you would want a diagonal and eyepiece, which are lacking here. It does not come with any finders either, which means you would have to purchase one, adding to the total cost.
- The cost is quite high for such a small telescope, which is a major deterring factor for anyone willing to get a telescope like this. But what advantages would you get out of a Mak, specifically this one?
Why would you want this scope?
This scope, as hinted to earlier does not cater to many people, thanks to its restrictive focal length, small aperture, and price. However, these telescopes still sell. Why is that, and why might you want one of these?
To put it simply, it is the optical quality people are accustomed to with Mak telescopes. Mak telescopes are well known for having excellent optical quality, which is crucially important for planetary observing, what you are likely to use this telescope for. The scope also has a relatively small central obstruction, which improves the quality of planetary views. The scope also shares the gift of being relatively small and light with SCT telescopes, which can be great for people who want a more portable setup.
Overall, in my opinion, the Orion 7” Mak telescope is one for not very many astronomers because of its long focal length, relatively small aperture and high cost. But those who are interested in having a small, light and portable planetary setup without having to use a Barlow lens or a long telescope should definitely consider Orion 9969 180mm Maksutov-Cassegrain Telescope, especially if they are looking for high-quality optics and a small central obstruction.