Celestron CGEM II EQ Mount and Tripod

A 40 lb Platform for SCTs up to 11 Inches

The CGEM II carries 40 lbs. Features include high-torque motors to smoothly drive heavier loads, low-cog DC servo motors, permanently programmable periodic error correction (PPEC), a dedicated autoguider port, large, easy-to-access polar alignment knobs and an ergonomic design that disassembles into compact, portable pieces. The latitude range is 15° to 70°, and the mount slews at nine speeds, tracking at sidereal, solar and lunar rates.

The CGEM II is designed to be ergonomically friendly, with large altitude and azimuth adjustment knobs for quick and easy polar alignment, and internal R.A. and DEC motor wiring for a clean look and an easy, trouble-free setup. The saddle connects directly to both CG-5 and CGE dovetail bars. Before attaching a tube, tighten both clutches and install the counterweight so the mount cannot move suddenly.

NexStar+ GoTo: 40,000+ Objects at up to 4.5° per Second

The NexStar+ hand control has a 2 line, 18 character backlit LCD and 19 LED backlit buttons, and its database holds over 40,000 objects, 100 user defined programmable objects and enhanced information on over 200 objects. New observers can start with the built-in Sky Tour, which finds the most interesting objects in the sky and slews to each one.

The mount slews at 9 speeds up to 4.5° per second and tracks at sidereal, solar and lunar rates in EQ North and EQ South modes. Alignment procedures are 2-Star, 1-Star, Solar System, Last Alignment and Quick Align; after a two-star alignment you can add calibration stars to improve pointing accuracy.

The hand control's USB port connects to a computer for point-and-click slewing from software and for firmware updates; updating the hand control with Celestron Firmware Manager may resolve some problems. The mount's software is Starry Night Special Edition and the SkyPortal app.

All-Star Polar Alignment and a 15° to 70° Latitude Range

The latitude range is 15° to 70°. Polar alignment is done not by moving the telescope in R.A. or Dec but with the mount's altitude and azimuth adjustments; both azimuth knobs push against the alignment peg on the tripod head, so you may have to loosen one while tightening the other. A bubble level built into the mount helps you level the tripod.

All-Star Polar Alignment lets you polar align accurately using any bright star, even when the celestial pole cannot be seen. After a two-star alignment with at least one calibration star, you slew to a bright star from the Named Star list, ideally high in the sky and near the meridian, and choose Polar Align, then Align Mount. The mount syncs on the star and slews to where it should be if accurately polar aligned, and you center it with the mount's latitude and azimuth adjustments, not the hand control's direction buttons.

Imaging: Permanent PEC, Autoguiding and Tracking Past the Meridian

Periodic Error Correction improves tracking by reducing the amplitude of the worm errors. Recording PEC takes three steps: the mount indexes its worm gear, you guide with an autoguider for at least 10 minutes (one full worm revolution) while it records your corrections, and then you play them back. The mount retains the recording, and PEC is meant for advanced astrophotography and still needs careful guiding.

The CGEM II tracks well past the meridian for uninterrupted imaging through the best part of the sky. The R.A. slew limits can be set anywhere from 40° above level to 20° below, so the mount can keep tracking past the meridian without flipping, or stop before an imaging cable runs out of length, and the Meridian setting (Favor Current, Favor West, Favor East or Disable) chooses which side of the mount the tube stays on.

A dedicated autoguider port on the electronics panel takes an autoguider cable. The mount also has built-in calibration routines that compensate for the mechanical variation found in every German equatorial mount; running them is recommended, and most need doing only once.

Tripod, Power and Setup

The steel tripod has 2" (50.8mm) legs with graduated markings on the lower section and weighs 20 lbs (9 kg); with the mount, it adjusts from 1346mm to 1651mm (53" to 65"). An accessory tray and a hand control holster are included.

Power is 12V DC at 3.2 amps. The supplied car battery adapter plugs into a car's cigarette lighter outlet or a portable power supply, or you can use one of Celestron's optional AC to DC adapters; use only adapters Celestron supplies, as others may damage the electronics and void the warranty.

To balance in R.A., loosen the R.A. lock lever with the counterweight bar horizontal and move the counterweight until the telescope stays put; in Dec, loosen the DEC clutch with the tube level and slide the tube in the saddle. Celestron's tip for imaging is a very slight imbalance, toward the counterweight side when the tube is west of the mount and toward the tube when it is east, so the worm gear always pushes against a slight load.