The Maksutov optical design is recognized for being a portable design that is easy to use and has a variety of applications, making it an excellent choice for both terrestrial and astronomical usage.
This C90 Mak has excellent optics with razor sharp images over a wide field.
Peter Besenbruch –
My unit was defective. It had an off center primary baffle tube. This resulted in poor illumination on one side of the eyepiece field. That said, I can make the following observations:The optics were sharp with the supplied eyepiece. The eyepiece looks like a GSO/Celestron Omni Plössl, but with standard, not multi-coatings. As such, it’s not bad. The one difficulty is that the opening in the baffle tube (16mm) is not wide enough to support the full eyepiece field. The outer 5-10% of the field simply goes dark. Skywatcher sells the same optics with a 25mm Plössl, a better choice. In addition, discussions on astronomy themed web sites, indicate that the C90 may have a longer focal length than stated. Closer to 1450mm, rather than 1260. Still, what’s there, looks OK. Contrast isn’t super, but a dew shield from Astrozap helps, as does flocking the inside of the primary baffle tube.The finder isn’t the greatest. I can’t see any way to focus the cross hairs. They look somewhat sharp using the near focus lenses of my trifocals. The straight through style works for terrestrial viewing, but far less well when pointing the scope at the stars. An Orion 6×30 Right-Angle Correct-Image Finder makes for a good, drop in replacement.This is a Maksutov design. They never do low power well, and a 40x or 50x low power (depending on which focal length you believe) is rather high for terrestrial viewing. There is a way of improving this, but it will cost you. You need an adapter that lets you use standard Schmidt-Cassegrain accessories, a Celestron f/6.3 Reducer Corrector, and a Celestron 1.25-Inch Visual Back. This reduces the low power magnification from its titular 39x to 25x, while cutting the unilluminated part of the eyepiece field by more than half. You get something close to a 2 degree field of view, and it’s sharp.So there you have it, a cheap, flawed scope that you can spend more money on and improve.10 December 2016 Update: One of three screws to hold the primary mirror and focus assembly was snapped off at the factory, stuck back in the hole, and then scope was sent on its way. With a 100% defect rate over two scopes, I am removing a star.14 December 2016 Update: A third scope has arrived. It, too, is defective. The front half inch of the primary baffle is very shiny, because Synta, the manufacturer, never bothered to paint that bit flat black. Rating reduced by another star, as this is inexcusable.Fixing the baffle flaw with the baffle fix worked fine, but the scope has an additional problem, spherical aberration. The C90 will not come to focus at 100x. Images below that looked washed out. Star testing shows extreme unevenness on either side of focus. This was one of the worst star tests I have seen in 50 years of viewing. This third scope is going back.Edit 10-2017: I picked up an Orion (U.S.) 90mm Maksutov in December, 2016. Like the C90, it is made by Synta. It, too suffers from an off center baffle. The flaw is nowhere near as serious as in the first sample of the C90. Still, it’s bad enough that if you want to check collimation using the daytime reflection method, you will get wrong results. I eventually collimated using a star. The result is a scope that is sharp at 160x. Contrast is quite good, even without a dew shield. It has proven to be a good travel scope. It provided nice views of the sun during the August 2017 eclipse, easily showing the sun’s granulated surface.
Peter Besenbruch –
Michael Laferriere –
For what this scope does, it weighs practically nothing. Celestron is marketing this as a spotting scope which gives you a limited lifetime warranty. I would avoid any of the used ones as Celestron has said this is only for the initial owner. At $150 the $20 you will save on a used one may not be worth it, especially if you need support down the road.As of the date I ordered it, this scope no longer comes with the tripod. The tripod kit & scope is still available at a slightly higher cost and the tripod can also be purchased separately from Celestron. Most of the reviews say the included tripod was barely adequate and they seemed inclined to replace it with a sturdier tripod. For accessories you get the nylon backpack carrying case, a 32mm plossl eyepiece (not bad for an included eyepiece & gives you a 39X view), a 45° erecting diagonal, and finally an 8X21 finderscope. The finderscope can be easily replaced as it uses a semi-standard guide mounted dovetail and can be replaced with Celestron, or Orion products such as the 50mm guide scope and other products as well. With its long focal length of 1,250mm you WILL need a firm steady heavy tripod for any kind of viewing. A photo tripod, even with the legs unextended may still wobble enough where it will make focusing and using this telescope a serious chore. Making focusing a bigger chore, this telescope also has a narrow depth of field. That is, if you aim at a tree a few miles away, you may see the middle of the tree in focus while the further and closer parts may be blurry. I did mount this on my Celestron CG-5 Computerized German Equatorial Mount 91518 and it worked like a charm on the night sky and became really pleasant to focus and work with once on a firm enough mount. It does appear the interior may not be baffled as well as some other scopes. If you are nearing a bright object like Spica, Saturn etc. you will see a stretched out circle pointing towards the object. This however, does make it easier to find the object you are looking for. Adding an aftermarket dew shield will probably help with this if it bothers you. AstroZap Flexible Dew Shield For Meade ETX 90 and Celestron C-90 Telescopes AZ103 As I mentioned the C90 currently comes with one eyepiece, a 32mm plossl which will yield about 39X. This eyepiece will enable to you to see Saturn’s rings when properly aimed and focused. I did use a Explore Scientific 6.7mm eyepiece which yielded about 187X which would be considered the ‘upper limit’ in magnification for this scope. Even though the night was windy and it was a hazy night this scope did a better job that I expected and it was able to easily view Saturn’s rings! While mounted on firmly on the CG5 (the C90 has a dovetail with two standard 1/4X20 holes for use on photo tripods and three holes drilled for use on standard astronomy mounts) was a dream to focus. I actually found it easier than my Explore Scientific 102mm f/7 Air-Spaced Triplet ED Apochromatic Refractor Telescope and didn’t even bother to use my Farpoint FP401 Bahtinov Focus Mask for Telescopes with Dew Shield or Front End Diameter from 3.5″ to 6.5″ when focusing on stars. This was just as easy to focus with an eyepiece or with a Canon 7d DSLR attached. The C90 comes with threads that will fit a standard T ring, so you do not need to order a T-adapter to use this scope at prime focus. When ordering a ring, make sure you don’t order an M42 ring as the thread size is the same but one is a finer thread. They will connect up together but will only go on for one or two threads and if you force it, you will be cross threading and ruining one or both of your devices. Note, the 7D when directly attached to this scope for prime focus photography, the moon will just about fill the entire frame of view on the 7D and other camera’s with a similar sensor size.I will be updating this review once I get a steady alt/az mount for bird watching & terrestrial viewing.All in all, I am pleasantly surprised with this scope as it has exceeded my expectations!
Michael Laferriere –
NJ Reviewer –
I’m using this at the rifle range for spotting. Super clear out to 200 yds so far. Can easily see .243 hits on Shoot n See target but can also see hits t to the white backing board I use. I’m certain .223/5.56 round hits would also be easily seen at 200 Yds. This was with the 32mm eyepiece included with the scope. I plan to purchase an 8-24 Celestron eyepiece but if you have a 12mm already, that’s all probably all you’d need if you don’t mind using two or a looking at both close range and distant targets. Field of view is very good. I expect it to work well at 300 yds. Will update soon on that.My C90 sits on a Dolica GX600B200 tripod. I only extend the upper (thickest) legs and sit it to my left as I shoot. The combination of the the C90 and Dolica GX600 makes a solid enough platform.I used the included soft case to transport it. The Dolica tripod I purchased has it’s own soft case. Set up and break down is quick enough. The scope is protected enough in the soft case for rolling around in a car, but I wouldn’t do any drop tests on concrete. I don’t think there’s enough protection for a drop from table height to a concrete surface. If that’s a concern, look into a separate hard case. I just plan to be careful.After searching for a good spotting scope for the range and trying similarly price purpose build 60mm and 80mm scopes, I’m glad I purchased the C90. Field of view is better than others I’ve tried and the useful magnification you can get on this 90mm scope is better than the fixed 50x or 60x spotting scopes you’ll see. I’ll be testing at 500 yds over the summer and I expect good results. Will follow up on that as well. If you need something out to 1000 yds, by best guess is this may be ok, but a 120mm Maksutov might be a better choice.
NJ Reviewer –