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The German equatorial mount has long been the favored choice of astronomy buffs and astrophotographers because of its stability and portability. It is more stable because the center of gravity is directly over the center of its base, and more portable because it can be broken down into smaller component parts than a fork-mount telescope for easy storage and transportation.

For astrophotography, the German equatorial mount offers easier balancing; unlimited space at the rear of the telescope tube to mount a long camera equipment train that can’t bump into the drive base, as is the case with many fork-mounted scopes; and whole sky access that many fork-mounted scopes can’t achieve.

The Celestron CGEM – a Sky & Telescope Hot Product for 2010 – is a newly-designed heavy-duty computerized go-to German equatorial mount. The ergonomically designed CGEM has a fresh, attractive, bold appearance. It has 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 Sky & Telescope Hot Product citation said the CGEM mount offers “unquestionable value when it comes to Go To performance for astrophotographers and observers.”

The CGEM 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 1.5 amp 12 VDC power to operate. The maximum 1.5 amp power draw happens only briefly when accelerating to the high speed slewing mode from a standing start. 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.

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. If serious long exposure astrophotography is in your plans, an optional polar finder is available to increase the accuracy of your alignment.

The supplied 17 pound counterweight (one comes with the 8” CGEM800; two come with the 9.25” CGEM925 and 11” CGEM1100) is locked in place on the steel counterweight shaft with a single hand-tighten knob, making it easy to rebalance your scope in right ascension 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 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.

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.

The CGEM mount’s 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.

Optical tubes are installed on the CGEM mount using a slot on the mount head that accepts a Celestron CGE-style or Losmandy D-plate dovetail slide bar. This allows the optical tube to be quickly and precisely balanced fore and aft on the mount in declination, 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 CGEM mount weighs 75 pounds. The equatorial head is the heaviest component, at 41 pounds. The tripod weighs 17 pounds, as does the supplied counterweight(s) – one comes with the 8” CGEM800; two come with both the 9.25” CGEM925 and the 11” CGEM1100.

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