Celestron CGEM II Computerized equatorial mount, 40 lb. payload capacity 91523


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The 40 pound payload capacity Celestron CGEM II is a high performance fully-computerized go-to mount with a 40,000 star and object memory at a price that's easy to handle.

Our Product #: CGEMII
Celestron Product #: 91523
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Product Description

The Celestron CGEM II is an upgraded heavy-duty computerized go-to German equatorial moun. The ergonomically-designed CGEM II has a fresh, attractive, bold appearance – and a 40 pound payload capacity. This allows it to carry Celestron SCT optical tubes up to 11" in aperture, plus a full load of imaging accessories, as well as virtually any other optical tube and accessory payload less than 40 pounds in weight.

The CGEM II mount head contains dual-axis slewing/tracking motors on each axis for go-to computer control. Steel worm gears and 90mm diameter brass worm wheels assure long-term reliability and high accuracy performance. The use of low cog DC Servo motors with integrated optical positioning encoders offers smooth, quiet operation and precision slewing and tracking. The motor armatures are skewed to minimize cogging for precise jitter-free low speed tracking. The motor drives and their wiring are all internal, keeping them snag-free and free from dust and debris.

The mount requires a minimum 1.5 amp 12 VDC power supply to operate. The maximum 1.5 amp power draw happens only briefly when accelerating to, or decelerating from, the high speed slewing mode from a standing start with a small payload (8" SCT OTA or similar). Normal power draw with a well-balanced payload is generally less than half the maximum draw.

The mount comes with a car battery cord to operate from the cigarette lighter plug of your car or from a rechargeable 12V battery pack. The 17 amp hour capacity Celestron Power Tank #4517V is recommended and will operate the mount all night long without danger of running out of power. An optional Celestron #2338PRO 5 amp ac adapter is available to run the CGEM II all night from household AC in backyard or observatory.

To make a casual polar alignment for visual use quick and easy, there's a latitude scale with large ergonomically-friendly altitude and azimuth adjustment knobs. No polar alignment finderscope is available to aid in the precise polar alignment required for long exposure astrophotography, nor is any needed. A unique Celestron All-Star Polar Alignment program built into the NexStar hand control helps you do a very precise computerized polar alignment in mere minutes, using any bright star, even when Polaris is hidden by trees or buildings. It works in both northern and southern hemispheres.

The supplied 17 pound counterweight is locked in place on the steel counterweight shaft with a single hand-tighten knob, making it easy to rebalance a scope if you add heavy photographic accessories. If needed, optional counterweights are available to balance very heavy loads.

For observing or imaging objects near the meridian (the imaginary line passing directly overhead from North to South), the CGEM II is designed to track well past the meridian for uninterrupted imaging through the most ideal part of the sky.

There are nine motor drive speeds: 0.5x and 1x sidereal for guiding; 4x, 8x, 16x, and 64x for centering; and 1°, 2°, and a fast 5° per second for slewing. Preset tracking rates include sidereal, solar, and lunar. Equatorial tracking modes are available for both northern and southern hemispheres.

The supplied NexStar computer hand control has a built-in database of more than 40,000 stars and objects. These include the complete RNGC, Messier, Caldwell, IC, and Abell catalogs; selected SAO stars; the planets, the Moon, and others. The custom database lists of all the most famous deep-sky objects by name and catalog number; the most beautiful double, triple and quadruple stars; selected variable stars; non-planetary solar system objects; and asterisms.

You can also store and edit the right ascension and declination of 400 additional user-defined objects of your own choosing, such as the comet and asteroid coordinates published monthly in Astronomy and Sky & Telescope magazines. The computer control can find any of those objects with only a few keystrokes, and track them with high accuracy for visual or photographic applications. There is enhanced information on over 200 of the most note-worthy objects.

The NexStar computer control of the smooth and precise CGEM II go-to mount makes finding over 40,000 stars and objects easy and automatic, so you can spend more time looking at them, rather than looking for them.

New for the CGEM II mount, a USB 2.0 communication port on the hand control allows you to operate the telescope via a personal computer using a USB cable and NexRemote software CD-ROM. The hand control and motor control software is flash-upgradeable to allow you to download the latest product updates over the Internet to keep your CGEM II mount always at the cutting edge of technology. An autoguider port is located on the electronic pier for guided, but unattended, long exposure astrophotography.

The NexStar hand control provides a constant digital r. a. and dec readout of the scope's position on the sky. This provides much greater accuracy than conventional manual setting circles for star-hopping or locating objects by their celestial coordinates alone, should you want to observe the old-fashioned way without using the computer to find objects for you.

The software built into the NexStar hand control includes mount calibration, database filter limits, hibernate, five alignment procedures, user-defined slew limits, a new "All-Star" polar alignment routine that uses any bright star for a quick and accurate polar alignment, and more. Built-in adjustable backlash compensation permits precise corrections during astrophotography and when observing visually at high powers. A high precision pointing subroutine in the computer lets you point accurately at objects that you want to photograph that are too dim to be seen though the scope.

The software includes permanent programmable periodic error correction (PEC) to correct for the minor periodic tracking errors inherent to all worm drives that might otherwise mar your long exposure photographs. The CGEM II mount retains the PEC recordings when it is powered down. The hand control and motor control software is flash-upgradeable to allow you to download the latest product updates over the Internet to keep your CGEM II mount always at the cutting edge of technology.

An autoguider port is located on the electronic pier for long exposure astrophotography. The autoguider port can use a six-pin RJ-12 modular jack ST-4 compatible CCD autoguider to automatically control the drive motors during long exposure astrophotography.

Five different alignment methods are built into the NexStar computer - 2-star align, quick align, 1-star align, last alignment, and solar system align - allowing you to choose a level of computer accuracy in automatically finding objects with which you are comfortable. Alignment is easily accomplished in only a few short minutes. You can be observing in less than 15 minutes after you first take your CGEM II-mounted scope outdoors.

In addition, the NexStar computer hand control is GPS-compatible (using an optional inexpensive SkySync GPS module) for full GPS (Global Positioning System) satellite accuracy. Adding GPS to the computer is something no competitively-priced mount can do. Once the scope is approximately polar aligned, the 16-channel SkySync GPS system uses signals from government satellites to calculate the scope's location on earth with an accuracy measured in meters. The system also calculates the current time based on the split second accuracy of the GPS time signals.

After the SkySync quickly completes these calculations and enters the information into the computer control for you automatically, the computer can then orient the scope with the sky, slew to a pair of guide stars, ask you to confirm that the stars are in the center of the field (and center them if they're not precisely aligned), and then start finding and tracking over 40,000 objects for you at your command. With the CGEM II go-to mount and the SkySync, orienting your scope in time and space on earth and aligning it on the sky becomes almost as easy a task as simply turning the mount on.

The adjustable height tripod has 2" diameter stainless steel legs with a metal center leg brace for rigidity to provide excellent damping characteristics. The center leg brace is drilled to form a convenient accessory tray that holds 1.25" and 2" eyepiece to keep them up out of the dew-soaked grass.

New for the CGEM II mount is a dual saddle plate. The saddle plate will now accept both the CGE/Losmandy wide dovetail plate as well as the AVX/Vixen style dovetail plate. The dovetail slot on the top of the mount holds the long dovetail slide bar mounted under the optical tube. This allows you to slide the optical tube fore and aft in the dovetail slot to quickly and precisely balance the optical tube in declination when you add or subtract accessories, eliminating the need for an extra counterweight to balance a camera or other accessories. Setup and takedown times are exceptionally fast, as a single large hand-tighten knob holds the optical tube in place. A second lock knob prevents the tube from sliding off the mount should the hand-tighten knob loosen. The oversized dovetail mounting platform assures secure vibration-free tube attachment.

The CGEM II mount weighs 75 pounds. The equatorial head is the heaviest component, at 41 pounds. The tripod weighs 19 pounds, as does the single supplied counterweight. Optional 11 lb. and 17 lb. counterweights are available to balance heavy payloads.

Tech Details

Weight 75 lbs.
Warranty 2 years


Review by:
Not owned by me but a friend has one and it seems like a great mount. Capable to carry his Edge HD 8" and all the accessories. If your looking for something that is accurate and able to carry a decent payload I would recommend it. (Posted on 1/12/2019)
Review by:
I upgraded to the CGEMII from a fork-mounted C8 that was not very stable under the best of conditions. I have about 25lbs of gear loaded on it now and it's as solid as a rock. At 70lbs it's heavy but still light enough to be portable. The built-in alignment and polar aligning process takes about 20 minutes to complete and can be fine tuned with PEC and other function built-in to the mounts software. Highly recommended. (Posted on 12/24/2018)
Review by:
I bought an original CGEM from Mike/Astronomics several years ago. Handles a C11 without any trouble. I have mine pier mounted. Only quibble on the mount is that good alignment requires visually aligning a set of arrows on the RA and Dec axes, which usually means fumbling around with a flashlight in the dark. Once dialed in though, it does the work. I’ve done some planetary/lunar photography with it, and it’s steady enough. (Posted on 12/6/2018)
Review by:
I ordered mine from Celestron in April. As an astrophotographer who started from a CG5, this mount has been an excellent upgrade and in early tests allowed me to image M42's core at 2000mm for 20 unguided seconds with only a rough polar alignment.

I have since been using this mount for all my photography needs (at a more reasonable 400mm) and it tracks quite smoothly and precisely for both DSO tracking and planetary imaging. Only con is that the hand control cord is too short - with the RA tilted over to one side, the hand control starts to pull out of its holster. Just 6" more inches of cable would have been ideal (Posted on 11/21/2018)
Review by:
I got this mount along with my C9.25 SCT as my first GOTO setup. Very easy to setup and execute a polar alignment. The HC is very intuitive to use and you will quickly learn the buttons without having to look at them. I coupled this with the Celstron StarSense auto align system and I was up and running executing perfect GOTOs within 10 mins of setup. With it's 40 lb payload capacity it would make a superb AP mount and now that I'm looking into Ap I'm starting to regret that I sold it!! (Posted on 11/21/2018)
Review by:
I replaced the AVX mount with this CGEM II. I mounted the 9.25 Celestron Nexstar Evolution optical tube with the wider CGM dovetail and it performs admirably. The AVX was good, but this is way more capable. I have only had a couple of outings, but am well satisfied with the alignment and tracking. It is considerably heavier than the AXV but manageable. I would say that it is a good upgrade from the AVX. At this time, I'm visual only. (Posted on 11/17/2018)
Review by:
I have the original CGEM. Good solid mount for the price. The II does have some useful improvements. The QHY Polemaster is a helpful addition. (Posted on 10/7/2018)
Review by:
After struggling for years with a outdated mount that is too small for my scope "LX200ACF 10" I have decided that this is the mount for me. I like all the new features and it certainly has the payload capacity to carry my scope and accessories. I can't wait to order it and that can probably happen shortly after the first of the year. I need to sell some other toys first.. (Posted on 10/6/2018)
Review by:
I have, and will continue to recommend the Celestron CGEM as a starter mount for people who can afford something bigger than the Celestron Advanced VX but cannot afford Losmandy or better quality mounts. The price isn't prohibitively expensive like some of the other 'luxury' line mounts (Paramount, Astrophysics, etc) - and the functionality and ease of use are absolutely designed for a novice. The thoughtfulness of that alone is what will likely keep someone interested in astronomy. Frustration with equipment kills peoples enjoyment of this hobby and that is always a concern with the CGEM because I feel that the build quality is quite lacking, and there are some bad engineering choices. This mount does have it's issues, but they can be overcome if you know how to identify the issue you have, making this a capable mount after you've done your homework. Not to mention a healthy dose of some elbow grease from time to time. As for astrophotography, well, this mount works great with light loads, like a DSLR (pictured left) or a small refractor, and can carry large 11 inch SCT's for planetary photography.

My detailed review of the Celestron CGEM Mount is found at http://eastofjupiter.com/review-celestron-cgem-mount/ (Posted on 8/4/2017)
Review by:
I have been very impressed with this mount. One of the biggest things that impressed me were the GOTO's, they were dead on and hardly had to be moved. 10 minute subs are easy to get with a guider and good polar alignment. (Posted on 8/4/2017)
Review by:
As the Owner of a C10-NGT I have one of these mounts and I am very happy with it. The Mount has followed me from my home in the US to my new home in the UK and once reassembled was very easy to update via the small programs HC Update, PEC Update and the Motor Board offered by Celestron site.I rated this Mount as 5 stars because of the ease of use and assembly. (Posted on 8/4/2017)
Review by:
For the price this is a very good mid-range mount. I currently have it on a permanent pier with a C11 and imaging equipment. If properly polar aligned i can take 20mins exposures with round stars at 1750mm. You can't go wrong with this one.

Clear skies,
Javier Villarreal (Posted on 8/4/2017)
Review by:
I have owned a CGEM for 2+ years now. It is my primary astrophotography mount using scopes from 65mm to 10" in diameter and up to 1600mm in focal length with exposures up to 12 min in length. GOTO's are always spot on and tracking is superb. I really like the All-Star Polar Align as I take the mount with me to dark sky sites and it makes it so much easier and quicker to get a good polar alignment. A very capable mount at a good price. My only complaint would be the saddle and azimuth knobs are very hard to turn with gloves but aftermarket ones were very affordable and moved this mount form a 4 to a 5. Highly recommended! (Posted on 8/4/2017)
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