Post by patrickm on Sept 27, 2010 12:19:09 GMT -6
Last night we discovered that we couldn't balance the scope in declination, or even get close. We slid the scope all the way forward in the mount, and no luck even with Joe's five pound ankle weight resting on the front. People smarter and much more experienced than I were even more puzzled. Joe wanted to try to balance a 75lb sack of Quikrete he happened to have, but I demured. 
A bit of research shows that we really didn't have the scope all the way to the front! We had it all the way forward to the rear set (safety) screw. The set screw is there to keep the thing from sliding off the front of the mount. (Steve called it the "Oh sh|t! screw. And 5 minutes later saved the whole tripod from falling over because I hadn't REALLY tightened the leg screws. Not used to all this heavy stuff!) There's another near the front to keep it from sliding off the back and turning into a big pile of broken glass and aluminum. Will give it a whirl and remember not to slew below horizon to view center of Earth, or turn off the software vertical slew limiter! Also found a little SCT counter weight that I assume hangs in place of the front set screw, but will give it a whirl this way before spending more money on it.
Celestron says:
A bit of research shows that we really didn't have the scope all the way to the front! We had it all the way forward to the rear set (safety) screw. The set screw is there to keep the thing from sliding off the front of the mount. (Steve called it the "Oh sh|t! screw. And 5 minutes later saved the whole tripod from falling over because I hadn't REALLY tightened the leg screws. Not used to all this heavy stuff!) There's another near the front to keep it from sliding off the back and turning into a big pile of broken glass and aluminum. Will give it a whirl and remember not to slew below horizon to view center of Earth, or turn off the software vertical slew limiter! Also found a little SCT counter weight that I assume hangs in place of the front set screw, but will give it a whirl this way before spending more money on it.
Celestron says:
How do I balance my CGEM-mount optical tube assembly (OTA) in declination?
Answer
To balance any OTA on a mount in declination, you need to slide the tube in the saddle rings or clamp perpendicular to the direction of the declination axis itself.
Most Schmidt -Cassegrain telescopes (SCTs) are heavy towards the mirror of the tube. Because of that, the tube must be moved towards the mirror end in the clamp of the CGEM mount.
The dovetail rails or bars for the CGEM OTAs have safety screws on either end to prevent runaway slides of the tube from the clamp. They are located approximately an inch in from the end of the orange dovetail bars.
In order to achieve balance in declination, you will probably have to slide the dovetail bar until the end of the bar is flush with the clamp. The mirror end or lower safety screw must be removed in order to do this.
After mounting and balancing the tube in declination, be careful not to orient the tube pointing down, since the lower safety screw prevents sliding in this direction.
This curse stuff is pretty heavy——defying Sri Tom Skilling, AccuWeather, and CCSC. Dag. 
