Celestron NexStar 90 SLT 90mm go-to altazimuth Maksutov-Cassegrain


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The NexStar 90 SLT (Star Locating Telescope) is an affordable go-to 90mm Maksutov-Cassegrain with high contrast/high resolution catadioptric optics that folds a 49" optical system into a 12" tube.
Our Product #: NS90SLT
Celestron Product #: 22087
Recommended Accessories

Product Description

You don't have to know how to read a star chart - or even know which way is North - to find your way around the sky with the Celestron 90SLT 90mm go-to Maksutov-Cassegrain. It has Celestron's famous SkyAlign easy alignment technology and a StarPointer red dot LED finder to make lining up on the sky a breeze.

Once aligned, the scope's computer hand control will find more than 4,000 celestial objects for you and will track them unerringly all night long while you observe. With its pre-assembled adjustable height steel tripod and easy no-tool assembly, the NexStar 90SLT can be up and ready to take you on a tour of the Universe in a matter of minutes.

The 90mm (3.5") Maksutov-Cassegrain folded catadioptric optical system of the NexStar 90SLT provides exceptional high contrast/high resolution solar system images - major surface details on Mars; multiple storm bands on Jupiter; even Cassini's Division in the rings of Saturn frequently popping into view in good seeing conditions; and more. Outside the solar system, the high resolution Celestron 90SLT splits close binary stars with ease, resolves open and globular star clusters, reveals the brighter nebulas and galaxies, and more.

The NexStar 90SLT has all the features and optical performance needed to keep a casual backyard astronomer happily observing for years. And it can be used for terrestrial observing, too - birdwatching, scanning the scenery from the home with a view, and more.

This Telescope's Optical System . . .

Maksutov-Cassegrain optical system: Aluminum tube 90mm aperture (1250mm focal length f/13.89) folded lens/mirror catadioptric. The system's Maksutov corrector lens is fully coated on both sides with antireflection material for high light transmission and good contrast. A no-tool quick release dovetail connects the tube to the mount for fast set-up and take-down.

Red dot finder: StarPointer non-magnifying variable brightness red dot finder on a quick-release dovetail mounting bracket. The StarPointer is a quick and easy way to point your telescope exactly to the desired object in the sky. There's no need to worry about the inverted images you see through traditional finders. Just align the red dot seen in the StarPointer with the desired star in the sky and you're done.

Internal focuser: Focuses by moving the primary mirror fore and aft in the optical tube by means of a focusing knob on the rear cell.

Star diagonal: 1.25" 90° prism type

Two 1.25" eyepieces: The first is a 25mm providing 50x. The eyepiece field of view is 1° across, twice the diameter of the full Moon for expansive views of the Moon, star clusters, and terrestrial observing. The second is a 9mm providing 139x for close-up views of the Moon and planets, globular star clusters, binary stars and more.

This Telescope's Mount . . .

Fork mount/drive system: Single fork arm altazimuth design with pre-installed internal dual DC servo motor drives. A compartment in the drive base accepts eight user-supplied AA batteries for powering the telescope. Selectable lunar, solar, or sidereal (star) tracking rates, with nine different slewing and centering speeds for locating objects (3°/sec, 2°/sec, 1°/sec, and 64x/32x/16x/8x/4x/2x the sidereal rates). For more details, click on the "SLT mount" icon in the support tab above.

NexStar computer control: The supplied computer hand control has an illuminated numeric keypad and a two-line 16-character LCD display. It has a database of 4,033 stars and objects, including the complete Messier and Caldwell catalogs of famous deep space objects; a selection of the brightest and best deep space objects from the Revised New General Catalog (NGC); selected SAO stars, including the best variable stars and multiple star systems; the planets; the Moon; and more.

With the built-in SkyAlign technology, lining up your 90SLT on the sky each night takes only minutes. Simply input the date, time, and your location into the computer hand control, then use the StarPointer red dot finder to align the telescope on any three bright stars, or to two stars and a bright planet or the Moon. The NexStar computer will automatically align itself with the sky. Then, it takes only a few keystrokes on the computer hand control to have the scope move automatically to your night's first observing target and start tracking it so you can observe at your leisure.

You can find hundreds of fascinating deep space objects your first night out, even if you have never used a telescope before. No matter what level of experience you start from, your NexStar SLT scope will unfold all the wonders of the Universe for you, your family, and your friends. For more details, click on the "SLT computer" icon above.

Adjustable height tripod: The preassembled tripod has stainless steel legs to damp vibrations quickly. The center leg brace holds a convenient no-tool quick-release accessory tray to keep your eyepieces and accessories up and out of the dew-soaked grass. The height adjustment lock levers are on the inside of the legs to avoid snagging your clothing on them in the dark.

Two-year warranty: All Celestron telescopes have a two-year warranty, double that of competitive scopes.

Tech Details

Aperture 3.5"
Focal Length 1250mm
Focal Ratio f/13.89
Highest Useful Magnification 208x
Motorized Controls Computerized GoTo
Weight 12 lbs.
Resolution 1.29 arc seconds
Supplied Eyepiece 25mm and 9mm 1.25"
Telescope Type Maksutov-Cassegrain
View Finder StarPointer
Visual Limiting Magnitude 12.3
Warranty 2 years


Review by:
I mainly purchased the Celestron 90 SLT for the GoTo mount only, but it turns out the small 90mm Maksutov is a solid performer.

My copy came with, dare-I-say, near perfect collimation and after two years of use a a few bumps here and there, collimation is still spot-on. This little one displays good planetary views and does well with doubles within it's light grasp, and it's not afraid of a little extra magnification--within reason, of course. The 90 has since become my Planetary grab n' go rig, sans the clunky SLT GoTo mount...

The SLT GoTo mount, well, it worked great with the 90 Mak mounted. No major issues with alignment or tracking, then I mounted an ES 127 Mak (similar is weight to the Celestron 127 Mak that also ships with the SLT mount) and tracking started to skip and lag, then slewing became labored and jerky. The SLT mount claims an 8 lb payload, Celestron claims a few pounds more, my ES 127 with accessories clocked in at 7 lbs 14 oz and the SLT mount could not handle it. I returned the 90 Mak to it's SLT mount, and though the mount is less labored in all it's motorized regards, it cannot be used as a reliable tracking goto anymore...

Celestron 90mm Mak tube -- 5 Stars!
Celestron SLT GoTo mount -- 2 1/2 stars if you keep the payload light.


J (Posted on 7/22/2019)
Review by:
Celestron seem to have a formula for entry/mid level small telescope packages. At this low price point, I think they assume the user doesn't know a ton about astronomy yet. So they give you a mount that does a fair job, but pair it with a cost savings optical tube.

I was able to find a 'shoe' that accepts a standard vixen dovetail bar, and swap it in place of the OTA. Then I bought a smallish spotting scope. The spotting scope has the advantages of bring fog free, waterproof, and gives a correct image. You can also use it for birding, shooting, other uses. For that reason, I give this 4 stars.

The mount itself is very nifty. Just a mediocre or poor optical tube that's maybe a 2-star item. (Posted on 1/3/2019)
Review by:
This diminutive little MAK packs a pretty good punch, visual wise. My SLT 90 came very well collimated, and was a breeze to set up. Best for planets, moon and doubles. Add some anti-vibration pads to help the higher mag views stabilize. The SLT GO TO mount is basic, and has a database of 4000+ objects. 3 Star align works best for me, but make sure you have exact GPS coordinates to create a CUSTOM location, this will help out a lot. Lastly, the SLT mount is rated for 8 lbs. of gear, any more weight WILL tax the tracking. Fun Grab-n-go! (Posted on 10/16/2018)
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Supplied Accessories

  • 90mm fully coated Maksutov optics
  • Go-to computerized altazimuth mount with dual-axis DC servo motor drives
  • Pre-assembled adjustable height stainless steel tripod
  • Accessory tray
  • Hand control with 4,000+ star and object database for go-to operation
  • Internal AA battery compartment (batteries not supplied)
  • Battery-powered variable brightness StarPointer red LED non-magnifying finder (battery supplied)
  • Internal moving mirror focuser
  • 1.25" prism-type star diagonal
  • 1.25" 25mm eyepiece (50x)
  • 1.25" 9mm eyepiece (139x)
  • TheSky Level X CD-ROM star-charting software
  • NSOL software for controlling the scope from a laptop or PC
  • Dust covers.