The Celestron 21088 Omni XLT 102 telescope is a traditional refractor style telescope which hobbyists and astronomers alike will be able to appreciate.

Celestron Omni XLT 102

The Celestron Omni XLT 102 (source)

With a good quality 4 inch lens, this scope has a lot to offer the beginner with a little more money to spend, but also makes a strong upgrade if you’ve been using a smaller and cheaper refractor.

With the Omni XLT 102, you’ll be able to take advantage of its 1000 mm focal length and German Equatorial mount to make the most out of its superb motion controls and easily track whichever heavenly bodies you please. It’s f/9.8 focal ratio makes it a ‘slow’ scope and so less prone to chromatic aberrations (which is a good thing) although, as you’ll see below, it does still have challenges in that department.

As our guide to telescope prices shows, the Omni XLT 102 (which is a 4-inch refractor) retails as expected for around $550. You can check today’s price on Highpoint Scientific (link opens a new tab).

The telescope body comes with a high quality CG-4 German equatorial mount. Its 1.75″ aluminium legs provide an incredibly sturdy and vibration-limiting mount that is a huge improvement on the mounts Celestron provides with their AstroMaster scopes, for example.

In this article, we’ll talk about the features of the Omni XLT 102 and examine the pros and cons of this telescope, including through the eyes of actual users.

Celestron Omni Specifications

Telescope Type:Refractor (achromatic)
Aperture:102mm (4 inches)
Focal Length:​1000mm
Focal Ratio:f/9.8
Finderscope:​​​6 x 30
Mount:German equatorial, 1.75″ stainless steel legs
Optical Tube Length:100c.m (39.5 inches)
Eyepieces Supplied:1 x 25mm
Limiting magnitude:12.5

Celestron Omni XLT 102 Pros and Cons

Celestron has been making telescopes since 1964.

The Omni XLT 102 is a refractor telescope mounted on a CG4 equatorial mount.

It has an aperture of 102mm, which is 4 inches, making it a decent-sized intermediate level telescope.


  • High quality mount
  • Lens coatings to minimize reflections
  • Great for planets, moon and stars


  • Not the best choice for faint deep space objects
  • Chromatic aberrations affect image quality

Overview of the Celestron Omni XLT 102

The Celestron 21088 Omni XLT 102 refractor telescope is the right tool for a more serious amateur astronomer.

The XLT is a seriously built telescope that could well last you for many years of backyard observing without complaint.

High Quality Mount

The high build quality of the Omni XLT 102’s scope, mount, and tripod put many other telescopes in the same price bracket to shame, as does its easy assembly and portability. 

The telescope breaks down into tripod and scope with a minimum amount of effort, which makes transporting it a lot easier. Keep in mind that the combined weight on mount and scope is over forty pounds – if you use all the counterweights on the mount – so you won’t want to have to move it far by hand every time you use it.

Part of the reason for the weight is the high quality equatorial mount. It is the very stable CG-4 model, which retails on its own at around $300 (check today’s price), which shows what a great price this combined mount/telescope package presents.

Best for Planets and Stars

Like most refractor telescopes, the Omni XLT is best used for solar system and stellar observations. The money you are spending on this four inch telescope could get you as much as 8 inches of aperture, if you were to spend it on a Dobsonian style instead.

You will see superb views of the moon, planets and even the brighter deep space objects. It will show off double stars particularly well, if that’s your game. However, if you are hoping to see fainter galaxies and nebulae, then you’re better advised to invest in a scope with a larger aperture which will gather in more light.

The Omni XLT 102 probably isn’t the right telescope for users who are interested in doing deep-field stellar photography with long exposure shots, either. The telescope itself is perfectly able to carry a camera or CCD, but the mount is a manual one and so not capable of tracking sensitively enough for the requirements of astrophotography.

That said, a tracking motor for the CG4 telescope mount can be fitted, financially it makes more sense to buy one already equipped for the job.

On the note of light gathering, the Omni XLT 102 has an interesting feature which users doubtlessly enjoy, perhaps without noticing. The StarBright XLT optical coating is on every optical element within the Omni XLT 102, and boasts as little as 3% light loss per lens, meaning that the user gets a brighter image at higher magnifications than they would with other telescopes without the coating.

Chromatic Aberration

The Omni XLT 102 is more than sufficient for viewing objects as distant as Jupiter’s moons with good resolution, but using the scope to resolve planets or moons at that distance will cause the user to bump up against one of the telescope’s quirks: chromatic aberrations. Chromatic aberrations are distortions in the image’s color due to the optical setup of the telescope itself and are inherent in any telescope with lenses (read more about chromatic aberrations here).

The chromatic aberrations on the Omni XLT 102 tend to be faint blue haloes around grayscale objects that reflect light but don’t produce any of their own, such as planets, moons, and meteorites—exactly where the scope is at its best use case. These can be reduced with good filters, if you feel the need.

These aberrations aren’t deal breakers by any means, though novice astronomers may become confused if they don’t have a good understanding of the phenomenon. When looking at stars or galaxies, there are no noticeable aberrations.