Celestron CGEM II
The CGEM II contains innovative new features such as the dual-sized dovetail saddle plate, graduated markings on the tripod legs, USB 2.0 connection on hand controller for PC connection, Permanent Periodic Error Correction, dedicated auto guider port and the ability to track past the meridian. The saddle assembly has also been lowered, moving the instrument package closer to the center of gravity.
Celestron CGEM II
How does the CGEM II mount compare with the Advanced VX?
In one word, heavier! This applies to both the capacity and the weight of the individual components. The equatorial head weighs 40 pounds for a CGEM II vs. only 17 pounds for the Advanced VX. The included counterweight is also heavier at 17 pounds vs. only twelve pounds for the Advanced VX. This added weight is a necessary consequence of the larger 40 pound instrument capacity. Imagers will want to keep this in mind, especially if a guide scope and autoguider could be in your future. Visual observers, on the other hand, should probably be content with the smaller Advanced VX mount when using eight inch Schmidt-Cassegrain or EdgeHD optics. We do recommend the CGEM II for visual users wanting either the eleven inch SCT or EdgeHD optical tubes, as either of these really challenge the upper limits of the Advanced VX mount's capacity.
Is the CGEM II suitable for imaging with eleven inch optical tubes?
This is a gray area because the weight of the optical tube and camera do tend to fall within the 40 pound instrument capacity of the mount. Adding a guide scope, autoguider and possibly a filter wheel will quickly approach that 40 pound limit. There is a rule of thumb in this hobby that says one should really aim to stay closer to half of a mount's instrument capacity when imaging, and that rule would certainly apply here. If your goal is to image with Celestron's eleven inch optics, we strongly recommend stepping up to their CGX mount.