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Celestron 21024 FirstScope Telescope Review

Celestron’s FirstScope is probably the only usable telescope that I’ve ever seen that retails for under fifty dollars. However, usable does not necessarily mean good, and that’s what we’ll focus on in this Celestron Firstscope review.

The Optical Tube

The FirstScope is a 76mm (3”) f/3.95 Newtonian reflector with a focal length of 300mm, and a spherical primary mirror. If you have done some basic research about telescopes you probably know that a spherical mirror won’t focus light correctly as a parabolic one does, and that is indeed the case with the FirstScope.

Funny enough, if the FirstScope were f/6 or so, thanks to its small size and shallow curve it’d actually have a mirror close enough to parabolic as to work quite well. Even an f/5 would be passable. But an f/3.95 sphere simply doesn’t work well. The spherical aberration with the FirstScope is about 550 nanometers (1 wave), or 4-8 times the maximum tolerance for a decent telescope depending on who you ask. If you’re wondering why Celestron didn’t just make the scope longer, it’s because the material cost would go up, and the increased box size and weight alone would make it impossible to market the FIrstScope at the price it is sold for.

Celestron Firstscope

At f/3.95, precise collimation is critical with a Newtonian. Unfortunately for FirstScope users, the primary mirror sits on a plastic plate that doesn’t allow for any kind of collimation. You have an approximately 50/50 chance of the scope coming in decent enough collimation to render a remotely usable image (well, as usable as can be with a 1-wave aberrated mirror). Thankfully, Celestron’s customer service is fantastic and they’re more than happy to exchange your scope for a better one. Even if your scope comes in decent collimation, however, you’ll have to be careful so as to not knock it out of alignment.

Oddly enough, the secondary mirror on the FirstScope is collimatable, but you’ll probably never need to adjust it.

The focuser on the FirstScope is actually more or less the same thing you see supplied on most cheap small Newtonians even four times its price – a plastic 1.25” rack and pinion. I’m impressed that Celestron was able to put something this usable on such an inexpensive scope – though I would rather have a bad focuser than uncollimatable, bad optics.

The FirstScope has no finder – you’re supposed to simply sight along the tube. With the mere 15x supplied by the included low-power 20mm eyepiece, this is easy enough but may take some practice.

The FirstScope’s tube is wrapped in vinyl adorned with the names of famous opticians, astronomers, and physicists throughout history – a nice touch. This was originally done when the FirstScope was brought out for the International Year of Astronomy in 2009 to celebrate the 400th anniversary of Galileo’s first discoveries with the telescope, and Celestron has kept it in the decade since.

The Accessories

The FirstScope comes with two eyepieces: A 20mm Huygens giving 15x and a 4mm Ramsden (“SR”) giving 75x.

The 20mm Huygens…. functions. The apparent field of view is extremely narrow (30 degrees), and the view is fuzzier than it already would be with a good eyepiece in the FirstScope. The Huygens design adds some chromatic aberration (something one should never see in a Newtonian) and the edge of the field of view contains aberrations I don’t even know how to describe.

The 4mm Ramsden is useless, being the same hated eyepiece supplied with Celestron’s Powerseeker line. It provides too much power for the scope (75x), the eye lens is tiny, it has zero eye relief, it doesn’t perform well with a fast focal ratio telescope like the FirstScope, and the field is slightly narrower than the 20mm Huygens. It also has an annoying tendency to get stuck in the focuser, the solution to which is to turn the scope upside down, loosen the screws, and shake it – preferably while above a garbage can, where it belongs.

You can buy an “accessory kit” for the FirstScope. All the kit contains is some more garbage Huygenian eyepieces, a useless 5×24 finderscope, and a cheap Moon filter which you plain don’t need and doesn’t work well anyways.

Celestron offers a “Cometron” variant of the FirstScope which is exactly the same, except with passable Kellner eyepieces and a useless 5×24 finderscope attached. If that’s all you can afford I would recommend it over the base FirstScope, but really I would strongly caution you about both.


The FirstScope comes on a simple tabletop Dobsonian mount to which it is semi-permanently attached. Altitude tensioning can be adjusted with a hand knob while azimuth can be adjusted by tightening or loosening the nut in the middle with a wrench or pliers. As to the smoothness of the mount’s motions, they’re pretty good, but it’s more or less irrelevant for a scope that is probably not able to handle more than 40x.

How Useful Is It, Really?

So, all that being said, what can you really see with the FirstScope?

Venus’ phases are visible (forget Mercury being anything but mush if you can even find it). The Moon shows its craters and a fair amount of detail. Mars is a fuzzy, small red dot at best, and at worst nothing more than a star. Jupiter’s moons are visible and Jupiter itself is a small cream-colored ball – with a higher magnification than the 20mm eyepiece you could maybe make out the equatorial band(s), but the Great Red Spot is invisible as are any other features. Saturn’s rings are visible at 15x as “ears” sticking out from the planet similar to how Galileo saw them, and higher power might show you the rings in their true form if you’re lucky. Saturn’s moon Titan is also visible nearby.

Forget finding Uranus or Neptune, because they look like nothing more than a star and you’ll be lucky to get in the general vicinity by sighting down the tube.

As for stuff outside the solar system, anything besides the Orion Nebula, Pleiades and maybe a few bright open clusters are going to be hard because of the scope’s small aperture, bad optics, and the lack of a finder. Even the easiest double stars are difficult to split with the FirstScope.

A pair of 10×50 binoculars will show you the same things in the Solar System that the FirstScope can but much sharper, they’re cheaper, they’ll do better on deep-sky objects, you don’t need a table, finding stuff is easier, and best of all, you can use them during the day for non-astronomical purposes – particularly good if you’re not sure if you’ll be interested in the hobby and don’t want to waste your money. If you can’t hold 10x50s steady, 7x50s or 8x42s will also suffice.

Bottom Line

All in all, do I recommend the Celestron FirstScope?

Not really. A pair of binoculars is better, period. If you either are incapable of holding binoculars steady or you/a loved one absolutely MUST have a telescope and you can’t afford anything better, it’s better than nothing, but it will be blown away by a pair of binoculars or even a half-decent tabletop Dobsonian with real eyepieces and a parabolic primary – or a cheap small refractor in most cases.

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