Celestron Omni CG-4 Telescope Mount and Tripod

A German Equatorial Mount

The Omni CG-4 is a German equatorial mount: once polar aligned, its axis of rotation is tilted parallel to the Earth's, so you follow the stars as they move across the sky with the right ascension (R.A.) axis. The manual lists ball bearings in both axes for smooth performance. Two slow motion control knobs (cables) make fine pointing adjustments in R.A. and declination; the longer one is for R.A. and fits either of the two R.A. shafts, and the declination knob goes on the shaft pointing toward the ground, within easy reach at the eyepiece. For rough movements, unlock the R.A. and Dec lock levers (counterclockwise) and move the telescope by hand. R.A. and declination setting circles, with a vernier scale on the R.A. circle, let you find objects by their coordinates.

Counterweights and Balancing

The mount comes with two counterweights, 7 lbs (3.2 kg) and 4 lbs (1.8 kg), which slide onto the counterweight bar and lock with their side screws; the safety screw at the end of the bar keeps them from sliding off. The manual lists the mount with counterweights at 21 lbs (9.5 kg) and the tripod at 12.5 lbs (5.7 kg).

Balance in R.A. first: with the telescope to one side and the counterweight bar horizontal, release the R.A. clamp gradually to see which way it rolls, and slide the counterweights until the telescope stays put. Then, with the R.A. clamp locked and the tube parallel to the ground, release the Dec clamp gradually, never letting go of the tube, and slide the tube forward or back in its rings until it stays still. Celestron says these are general balance steps that reduce undue stress on the mount, and that good balance is crucial for accurate tracking with an optional motor drive.

Latitude Adjustment and Polar Alignment

The latitude adjustment covers approximately 20 to 60 degrees. To raise the polar axis, tighten the rear latitude screw and loosen the front one; to lower it, the reverse. Celestron recommends making the final altitude adjustment against gravity, with the rear screw. For azimuth, move the whole tripod for rough adjustments and use the two azimuth knobs, which push against the tripod's peg, for fine ones. Once polar aligned, the mount itself must not be moved: you point the telescope only in R.A. and declination.

The easiest method, the manual says, is the latitude scale: point the polar axis due north using a landmark, level the tripod with the built-in bubble level, and adjust the mount in altitude until the latitude indicator shows your latitude. It can be done in daylight and limits the corrections you make while following an object. For a closer alignment at night, set the tube parallel to the polar axis (the declination circle reads +90) and adjust the mount in altitude and azimuth until Polaris is centered, which gets you within about a degree. The manual also describes finding the celestial pole, aligning in the southern hemisphere and the declination drift method for more serious work.

Finding Objects with the Setting Circles

To find objects with the setting circles, first align the R.A. circle on a bright star with known coordinates near the celestial equator: center it, then turn the circle until its coordinate lines up with the R.A. indicator (the zero mark of the vernier). Then look up your target's coordinates, move the telescope in declination and R.A. until the indicators read them, lock each clamp, and check the finder. The R.A. circle does not move with the telescope, so it must be realigned each time you use it, and the accuracy depends on your polar alignment. The vernier gives readings to one minute of R.A.

The Tripod

The tripod has 1.75" stainless steel legs and comes fully assembled, with an all-metal center leg brace that doubles as the accessory tray and pushes against the legs for rock-solid support. Its standard height is 33", extendable to a maximum of 47"; the manual notes it is most rigid at its lowest height. A metal alignment peg on the tripod head marks the side that faces north, and a bubble level is built into the mount.

Setting It Up

The manual suggests a first assembly indoors. Retract the azimuth screws, set the mount on the tripod head over the alignment peg, retighten them and tighten the mounting knob under the head; slide the accessory tray over the central rod and tighten its knob. Thread the counterweight bar into the Dec axis and tighten its lock nut, point the polar axis north, then fit the counterweights, the slow motion knobs and the polar axis cap. With the R.A. and Dec clutches locked, slide the telescope's dovetail bracket into the mounting platform, tighten the mounting knob and snug the safety screw.

Optional Accessories

For tracking, Celestron's manual names its Dual Axis Motor Drive (93522), designed for the Omni CG-4, which controls the tracking speed with four rates (1x sidereal, 2x for guiding, 4x and 8x for centering), and a polar axis finderscope with a cross hair reticle to speed polar alignment. Both are sold separately.