When it comes to the telescopes we review, our editorial board (which is comprised entirely of astronomers) make unbiased judgments. Please keep in mind that our performance rating system on this page is completely unrelated to any kind of monetary gain.
The Celestron C90 is a portable Maksutov-Cassegrain Telescope marketed by Celestron primarily as a spotting scope. We’ll be looking at the “new” version, rather than the classic version which shares very little in common other than aperture and general optical layout. The C90 has been lauded by many in the amateur astronomy community as “something for nothing,” and as a great budget option. A 3.5” Maksutov is a fairly small instrument and somewhat limited in light grasp and resolution, but the infamous premium Questar 3.5 has essentially the same optical specifications. In principle, a 90mm telescope should magnify up to 180x. How does the C90 stack up?
6/10: Recommended with reservations
Score Breakdown (out of 5)
Moon & Planets: 3
Rich Field: 1
Ease of use: 4
Read our scoring methodology here.
There are several other 90mm Maksutov Cassegrains on the market. The other ones by Synta likely have the exact same optics. The Orion StarMax 90 comes on a usable but barebones tabletop mount. The Orion Apex 90 is another version designed as a daytime spotting scope and is highly comparable to the C90, but a little lighter weight. The SkyWatcher SkyMax 90 is another offering with no mount, but with astronomical accessories. Orion and SkyWatcher also offer some larger Maksutovs, a 4” and 5” variety which will have better light grasp and resolution.
Celestron also sells the NexStar 90SLT, a 90mm Maksutov on a computerized Go-To mount. There’s also the NexStar 4SE, a 4” Maksutov on a better computerized Go-To mount.
The Meade ETX90 is another 90mm Maksutov, but with optics which are more reliably superb, comparable even to the premium and absurdly priced Questar 3.5 in all ways except for mechanical design and ergonomics.
But a telescope of another optical design entirely might be a better fit for most observers. A Newtonian reflector telescope may not be as compact, but for the same price as a C90 and an adequate mount, you can get a 6” Dobsonian, which will show more detail on planets and the moon and many more deep-sky-objects. There are some more compact reflectors as well, such as the Zhumell Z114, Zhumell Z130, SkyWatcher Heritage 130P/AWB OneSky 130, and SkyWatcher Heritage 150P. These are all tabletop Dobsonians with more light grasp and resolution than the C90, albeit with their shorter focal lengths they require more expensive accessories to reach high magnifications.
If you’re looking for a small, compact telescope for deep-sky-object viewing, say for example if you’re going camping at a dark site, I recommend the Short-Tube 80.
This was a tough review to write. With the reputation of the C90, I was expecting to like it a lot more than I do. The telescope is not something for nothing. The fact that I had to send mine back to get one with decent optics implies that the quality control could be a lot better. It is fairly expensive at the moment, It requires a fairly substantial tripod or astronomical mount to use at all, it requires new accessories to get full use out of it. It’s not a bad telescope, and it turns out there’s a lot that it can show you, and its views of the Moon remain genuinely spectacular. If you’re looking primarily for a spotting scope for hunting, birding, or other nature observing, but which is also capable of doing astronomy, this might be a good choice over refractors (which have chromatic aberration) or reflectors (which can’t be used with an erect image). But it’s not a great value for your dollar. For the price you’d pay for the telescope and a decent mount, there are better options.