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Celestron C90 Review

Last Updated: 06.12.21



Main advantage


The C90 model is a Maksutov-Cassegrain, and this optical design puts a lot of emphasis on mobility and it is suitable for use in schools and the military. This innovative design uses a fast primary mirror with a corrector lens at the front. It is very compact and manages to provide exceptional results for a fair price.

This model works very similarly to the Schmidt-Cassegrain and the main difference is in the shape of the corrector since while a Schmidt uses a nearly flat fourth-order curve on a very thin piece of glass, the Maksutov is highly curved and has a thick meniscus lens. The thicker lens allows this option to perform much better than the competition.

The high-quality construction and the use of premium materials allow this spotting scope to provide excellent results in a wide range of applications from range shooting and bird watching to nature gazing and casual stargazing.

While there’s no such thing as a perfect telescope, since even the most expensive ones have a few tradeoffs, this one is situated in a good place. The performance it offers is exceptional and it comes in a compact design that will make it extremely easy for you to take it with you wherever you need it.


Main disadvantage


Because of the Maksutov-Cassegrain design which relies on the use of a thicker lens which can be very expensive to produce, Celestron had to make a few compromises on the rest of the unit in order to keep the price at a competitive level. The most important missing feature on this model is the waterproof rating.

While for some people it might not be a huge deal since, after all, you’ll probably avoid taking this out in the rain anyway since it is hard to go nature gazing or hunting in those conditions, it’s still something that we can’t ignore. Most models in this price range do come with this feature, and the lack of waterproofing on the C90 really sticks out.

Furthermore, since waterproofing also helps prevent condensation, users will do good to avoid using the product in extreme humidity since prolonged usage in such conditions can lead to damage.

Other than that, there is not a whole lot to complain about this model since it does bring up a lot of exciting stuff to the table. Even if for people who like to have all the latest features in their portable scope the lack of waterproofing might act as a deterrent, for the average user we don’t expect this disadvantage to affect the experience of using this scope too much.


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Main features explained


Great performance

When looking at scopes, one of the key features to consider is the size of the objective since it is the part of the product that gathers light and brings it into your eyes. The larger the objective lens, the more light the instrument will be able to collect, and the better you will be able to see.

The C90 model boasts an objective lens with an impressive diameter of 90mm. To make it easier for you to understand why this is a big deal, all you need to know is that most scopes in this range have an objective lens of 40 to 80mm.

An objective lens of 80mm is more than enough for multi-purpose usage especially in products that are designed to be compact and can’t always fit large lenses. The C90 spoils its users with the 90mm which helps it perform marvelously in any lighting condition. The lens can gather more light and that will make the instrument usable even in low-light environments.

Objects will appear sharper, brighter and with a higher resolution. The advantage of having a larger resolution is most evident when zooming in on distant objects since fewer details will be lost and you will get an overall crisper image even when zoomed all the way in.


Good magnification

For beginners in particular magnification is very important and while high-magnification shouldn’t be on the top list of your priorities, when coupled with premium optics it can provide some breathtaking results. The focal length of a scope divided by the diameter of its eyepieces gives it the magnification.

In the case of the C90, you get the benefit of a high focal length of 1250mm and an eyepiece of 32mm. Once you do the math, you end up with a default magnification of 39x (1250mm/32mm). For most applications 20x to 30x works perfectly, especially with poorer optics since it allows for little detail to be lost.

However, with this model, you won’t lose any details even at maximum magnification thanks to the large objective lens that outperforms other optical devices in this category. Furthermore, you can even mount it on a tripod to make better use of the high-magnification while maintaining a stable viewing experience.

For a compact instrument, the 39x magnification is at a sweet spot since it allows you to view even the more distant objects while maintaining great visibility and stability. This model accepts a wide range of mount eyepieces which means that you will be able to customize the magnification to suit your needs.


Small and versatile

This option manages to offer high aperture, long focal length, and excellent magnification without ending up being a huge scope that can weigh you down. Because it uses a Maksutov-Cassegrain design, the C90 uses a unique technique that allows it to pack a higher focal length in a much shorter tube.

Thus, you end up with a scope that measures only 16 inches in length but packs optics that you usually find in 50-inch models. It is also very light at just 4.63 pounds, which will allow you to take it with you wherever you go in the included backpack style soft carrying case.

The unit also comes with both a dovetail rail and a ¼-20 threaded mounting port which allows it to be mounted on both camera and astronomical tripods. Amateur photographers will enjoy this extra feature especially since it is very easy to make the switch to the camera tripod adapter.

Lastly, you also get multiple accessories included with your purchase which should help you make the most out of your new telescope.


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Ioana Moldovan

Ioana’s professional experience in the optics field has helped her understand the value of passing her knowledge forward. Her curious personality helps her gather useful information for her readers and her goal is to make technical information fun and accessible to everyone.

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