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Orion Telescopes
Orion StarSeeker III 90mm GoTo Mak-Cass Telescope
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  • The most portable StarSeeker III Mak-Cass lets you take a guided tour of the cosmos wherever you roam
  • Huge GoTo database of over 42,000 objects for a great view on any clear night
  • 90mm Maksutov-Cassegrain design packs a lot of magnifying power into a small, portable telescope
  • Once an object is located, the StarSeeker III 90mm will automatically track it so you can relax and enjoy the view
  • Includes 25mm and 10mm 1.25" eyepieces, 90-degree diagonal, EZ Finder II reflex sight, and more

Learn more
Item #  10066

Take a guided tour of the cosmos without leaving the comfort of your own backyard!

The self-pointing Orion StarSeeker III 90mm GoTo Maksutov-Cassegrain Telescope will show you and your family interesting celestial sights on any clear night. Its compact 90mm Maksutov-Cassegrain optical tube assembly makes it the most portable member of the StarSeeker III family of GoTo telescopes. What's more, the StarSeeker III 90mm features a smaller altazimuth mount than its brethren for easy transport. The most portable StarSeeker III boasts a long 1250mm focal length and f/13.9 focal ratio for exceptional high-power performance.

An excellent choice for intrepid beginning amateur astronomers, the user-friendly, fully computerized StarSeeker III 90mm GoTo telescope provides electronic, motorized navigation to all the finest celestial objects. StarSeeker III models boast an upgraded computerized database of over 42,000 celestial objects to explore. Once the GoTo system locates a selected object, the StarSeeker III 90mm Mak-Cass will precisely track it as it appears to move across the night sky, so you can enjoy the view for as long as you like before selecting a different target. This allows you to relax and enjoy the view instead of fumbling with cables and buttons to keep the object centered.

Lightweight at just 10.7 lbs. when fully assembled, the easily portable StarSeeker III 90mm GoTo Maksutov-Cassegrain packs a big performance punch in its small telescope tube. Maksutov-Cassegrain telescopes employ both mirrors and lenses to "fold" the light path, which keeps them conveniently compact in size, but with the high magnifying abilities of much longer refractor or reflector models. This gives the StarSeeker III 90mm Mak-Cass a winning combination of easy portability and powerful optics. What's more, the included single-arm GoTo altazimuth mount can be set-up and taken down quickly, and features a quick-release dovetail saddle for swift telescope attachment without the need for tools.

Following an easy two-star alignment process, the StarSeeker III 90mm GoTo can take you on a guided tour of the best visible objects in the night sky. Once aligned, this smart telescope will find and aim itself at any visible planet or Messier, NGC, or IC catalog object in seconds with just a few button pushes. Built-in encoders and servo motors slew the telescope accurately and automatically right to the object you select from the GoTo hand controller's intuitive menus. With a vast database of over 42,000 celestial objects, the StarSeeker III 90mm GoTo Mak-Cass will show you interesting sights on any clear night. 

Since the StarSeeker III 90mm Mak-Cass can locate and track celestial objects with its motorized GoTo system, you can use it along with a camera or smartphone to take impressive pictures of the night sky. Capture stunning snapshots of the Moon, planets and more by attaching a dedicated astrophotography camera, or a combination of an Orion SteadyPix accessory and your own point-and-shoot camera or smartphone to the StarSeeker III 90mm Mak-Cass to explore the rewarding hobby of astrophotography. (Cameras and SteadyPix accessories sold separately.)

You'll get a great assortment of useful accessories with the StarSeeker III 90mm GoTo Maksutov-Cassegrain telescope:

Two 1.25" eyepieces are included with the StarSeeker 90mm GoTo Mak-Cass.

The included 25mm Explorer II eyepiece provides 50x magnification in the 90mm Maksutov-Cassegrain optical tube, and the 10mm yields 125x for higher-power looks through the telescope. We recommend starting with the 25mm eyepiece every night to observe a wider area of the night sky, then boost magnification by swapping out the 25mm eyepiece with the 10mm ocular once you have an object centered.

Use the included 90 star diagonal to view the night sky comfortably

A diagonal "bends" the light path of a telescope so you can enjoy the view without having to contort yourself into awkward positions to peer into the eyepiece. The 90 star diagonal that comes with the StarSeeker 90mm GoTo Mak-Cass places the eyepiece you're using in a comfortable position for nighttime stargazing of the skies above.

The Orion EZ Finder II reflex sight makes it "EZ" to center alignment stars.

Use the included EZ Finder II reflex sight to help center initial alignment stars when performing the two-star alignment required for accurate GoTo performance. It's a non-magnifying sighting device that superimposes a tiny, LED-powered red dot, focused at infinity, on the sky. After a simple alignment procedure, the red dot shows exactly where your telescope is pointed.

Let the computerized GoTo controller guide you on a tour.

The StarSeeker III 90mm GoTo Mak-Cass lets you explore the skies with pushbutton ease thanks to its GoTo hand controller. With a vast database of over 42,000 celestial objects including stars, double stars, galaxies, nebulas, star clusters, and more, the included computerized GoTo hand controller will become your tour guide to the skies.

The StarSeeker III 90mm GoTo Mak-Cass also includes a compass, PC interface cable, and a removable accessory tray for the tripod. Each StarSeeker III requires 8 AA batteries (not included) or an external 12V DC field battery or AC-to-DC wall adapter.


Limited Warranty against defects in materials or workmanship for one year from date of purchase. This warranty is for the benefit of the original retail purchaser only. For complete warranty details contact us at 800-676-1343.

Product Support
Visit our product support section for instruction manuals and more
  • Best for viewing
    Lunar & planetary
  • Best for imaging
    Solar, lunar & planetary
  • User level
  • Optical design
  • Optical diameter
  • Focal length
  • Focal ratio
  • Optics type
  • Eyepieces
    Explorer II 25.0mm,10.0mm (1.25")
  • Magnification with included eyepieces
    50x, 125x
  • Resolving power
  • Lowest useful magnification
  • Highest useful magnification
  • Highest theoretical magnification
  • Limiting stellar magnitude
  • Optical quality
    Diffraction limited
  • Finder scope
    EZ Finder II
  • Focuser
  • Diagonal degrees
    1.25" 90° Mirror Star
  • Secondary mirror obstruction
  • Secondary mirror obstruction by diameter
  • Secondary mirror obstruction by area
  • Mount type
  • Astro-imaging capability
    Lunar & planetary
  • Computerized compatibility
    Go-To included
  • Alignment procedure
    2-Star GoTo Alignment
  • Number of objects in database
  • Tracking rates
    Sidereal, Solar and Lunar
  • Power requirement
    8-AA batteries or 12-volt DC
  • GPS
    Sold separately
  • Backlash compensation
  • Available ports
  • Tube material
  • Tripod material
  • Tripod leg diameter
    2.00 in.
  • Height range of mount
    31.10 in. - 52.50 in.
  • Length of optical tube
    11.0 in.
  • Weight, optical tube
    3.2 lbs.
  • Weight, mount/tripod
    6.9 lbs.
  • Weight, fully assembled
    10.7 lbs.
  • Additional included accessories
    Objective dust cover, Starry Night software - digital download insert
  • Other features
    Accessory tray with single-knob attachment, Hand controller holder
  • Warranty
    One year

Orion StarSeeker III 90mm Mak-Cass OTA
StarSeeker III mount and tripod
GoTo hand controller
Orion EZ Finder II reflex sight
25mm Explorer II telescope eyepiece, 1.25"
10mm Explorer II telescope eyepiece, 1.25"
90-degree star diagonal
Liquid-filled compass to aid in GoTo alignment
Accessory tray
PC interface (serial) cable
Hand controller holder
Battery holder for 8 AA batteries (batteries not included)
Starry Night digital download insert

Orders received by 1pm Eastern Standard Time for in-stock item the same business day. Order received after noon will ship the next business day. When an item is not in-stock we will ship it as soon as it becomes available. Typically in-stock items will ship first and backordered items will follow as soon as they are available. You have the option in check out to request that your order ship complete, if you'd prefer.

A per-item shipping charge (in addition to the standard shipping and handling charge) applies to this product due to its size and weight. This charge varies based on the shipping method.

Standard Delivery: $0.00
Standard Delivery to Canada: $30.00
3 Day Delivery: $62.00
2 Day Delivery: $62.00
Next Day Delivery: $76.00

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