Winter is probably the worst time for stargazers. The air is foggy humid and the sky is mostly cloudy. For birdwatchers this is probably a great time to spot winter birds appearing in this select season. Regardless of the season, a spotting scope is a great piece of equipment to use in range shooting, birdwatching, casual stargazing or just admiring nature up close. They have magnifications greater than binoculars but less than telescopes. So this is probably the point where you decide what you aim to do with a scope before buying it. That said…
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The Good Stuff
You CAN use it as the perfect telescope Let’s be honest there’s no such thing as the perfect telescope. Even the most expensive one has trade offs. By definition spotting scopes are used more for terrestrial use and only casual star watching. However, despite being marketed as a spotter, the C90 Mak features make it great for astronomical use as well.
Aperture: The most important part in a scope is the objective. Or the main light gathering mirror or lens. We see things because of the light that bounces off them. The larger the objective the more light your scope can collect and the better you are able to see. The aperture (diameter of the objective mirror) of the Celestron C90 is a whopping 90 mm. It jumps from the normal range of 40 to 80 mm. While 80 mm is usually great for dual purpose viewings, the C90 spoils you with 90 mm. Objects appear sharper, brighter and with a higher resolution than other spotting scopes. Imagine switching to 1080p from 720p. A higher aperture also allows higher zooming-in quality.
Good magnification: This is never at the top of my list of priorities. However most beginners want a scope that can magnify highest. The magnification of a scope is given by the focal length of the scope divided by the diameter of its eyepiece. The Mak C90 has a high focal length, 1250 mm. The eyepiece provided with the scope is of 32 mm. So the default magnification is (1250mm/32mm) 39x.
For almost all observations 20x to 30x works perfectly fine. In fact any near to 60x or more, and your objects become invisible. This is because higher magnification applies to everything and not only the object. So dust, humidity particles, and slight movement, are all intensely magnified and what you see is mush. There’s a reason why the Hubble is placed in space.
39x would not be visible for most scopes with low quality optics, and would rip you off your money. But the C90 with its high aperture, outperforms other optical devices and aptly resolves and contrasts your magnified object. You don’t see mush. You see clearly defined, bright and sharp objects. And get excellent value for money.
Photography ease: This probably isn’t of much importance to viewers, but I love how Celestron has a built in T-adapter. Most people with Instagram accounts would use a camera attached to the telescope just as much they use their eyes. And the threaded metal makes it super easy to make the switch.
Small and portable Hobbyists are often extreme and go for highest aperture, longest focal length telescopes. Which lands them with humongous telescopes that weigh as much as their cars and are an immense challenge to carry or set up. The Celestron C90 is a Maksutov Cassegrain design that uses a technique of light-folding that permits a higher focal length in a shorter tube. So while a normal refractor telescope of 1250 mm focal length would be 125cm long, the C90 is only 40 cm. It also weighs only 2.3 kgs. I am a petite girl and I can carry that in one arm.
Sturdy One of the first things you will notice when you unbox the Mak is how solid it is built. I would say the Celestron guys have actually over-built it. With a complete metallic exterior the Mak C90 is sturdy and ruggedized to be used freely in the outdoors.
The Bad Stuff
Not waterproof Okay, so this might seem fine since you don’t skywatch when it’s rainy and animals are under cover then. But some like to ‘have it all’ in their portable scope and Celestron C90 is not waterproof. This also means that condensation from the hot, running scope in cold climates, or using it in extreme humidity might damage the scope.
Redundant finderscope Atop the scope is a finderscope with crosshairs for pin-pointing purposes. I see how this could be a useful feature in hunting and birdwatching. However it is redundant for celestial viewing. It is also cumbersome to view through. Specially if you wear eyeglasses. The eye relief (or the distance your eyes need to be from the eyepiece) of the finderscope, is not optimum. So if you wear glasses you may struggle using the finderscope. The good thing is it comes as an attache in the assembly so you can just leave it out if you dislike it as much as I do.
Narrow field of view as compared to telescopes. I know it isn’t fair to compare the C90 spotting scope with telescopes, but the astronomer in me thinks, ah what the heck. Mind you the difference in the field of view is very minimal. Not to mention that telescopes with high quality optics are much more expensive. So I can’t really complain.
General Stuff you need to know
It is important to mention that the C90 is great for eyeglass wearers who struggle to find the best eyepiece-scope combination. The eye relief of 20 mm is good enough to refocus light through glasses. It also has a good cooldown time so 30 mins before viewing is the suggested time to start setting up.
Celestron have also gone the extra mile in multi coatings on the corrector lens. Since this scope is catadiaoptric, there is only one corrector lens that could be coated to avoid incoming light reflecting back. And it is multi-coated.
In the specifications provided by Celestron on their official website, mentioning upright image as a feature wasn’t really necessary. All standard spotting scopes offer this capability.
In case you’re wondering, the 45 degree image erecting prism is a slanted prism located in the 45 degree slanted tube. It lets you change your viewing angle and comfortably view higher placed objects without having to stretch and strain your neck like you would have to with a straight-through tube. You also view the image upright. Pretty cool feature, if you ask me. Although I don’t really get why manufacturers mention them as two separate features.
A noteworthy feature for new buyers: the magnification on this scope can be varied by changing eyepieces. The smallest eyepieces available are 10 mm so you can achieve upto 1250mm/10mm=125x magnification. However, you will have to try and test the eyepieces with the scope to find the practical limit of magnification.
Although it is marketed as a spotting scope but the Mak C90 is a great telescope as well. Whether you’re a birdwatcher or a stargazer, it is equipped with high-end Maksutov-Cassegrain optics and has a large aperture of 90 mm that lets you view the sharpest and most resolved images for all purposes. However, rarely can you find a scope with the above qualities that is as small, portable and sturdily-built as the C90. A good scope is one that makes objects more visible, but to me additionally a good scope is one that I can easily carry, set up or mount and store. While every spotting scope has its tradeoffs, the Celestron C90 Mak is easily the best option out there for portability and high quality viewing.