Celestron C9.25 OTA and GM8 Mount

The Celestron C9.25 OTA is currently in limited production and is essentially hand made. Where on normally finds cast metal and plastic on a SCT, one finds machined metal on the C9.25. The focuser is dream to use. It has just the right tension - not too easy to turn and not too hard. The focuser digital read out is very accurate and repeatable. I could turn the focus knob several turns in either direction and then return to it to the focus readout value and the scope would be precisely in focus. If you are going to do imaging, this is a very valuable asset. The Optical Tube Assembly exudes quality. It is hard to believe that this OTA is made is made by Celestron.

The main mirror has about twice the focal length of an ordinary SCT mirror. This makes it easier to get a better mirror figure; however, to keep the system at f/10, the tube is longer (in relation to the diameter) than the typical SCT. Star tests of this telescope show that it is corrected to about 1/8 wave. It is truly amazing to see the pin point stars images produced by this telescope, particularly if you are used to the star images produced by other SCTs. Other C9.25 owners have reported similar results. The typical SCTs are corrected to 1/4 wave at best. Many are 1/2 wave. The 9.25" aperture is an ideal compromise in size. It provides more light than an 8" SCT, yet it is not big enough to be a handling problem for the average person. The Celestron C9.25 OTA may be one of the best kept secrets in the commercial telescope market.

The Losmdany GM8 is the ideal mount for this fine telescope. The mount is light weight in terms of handling, yet it can handle twice the C9.25 load with no problem. It is easy to transport, set up and take down. The built in polar alignment scope makes polar alignment a snap. Celestron sells the C9.25 OTA packaged with a mount that looks like the GM8, but it not a true GM8. The Celestron version has a flimsy and inadequate tripod. The precision ball bearings of the GM8 have been replaced with bushings in the Celestron version. You can buy a C9.25 OTA mounted on a real GM8 mount from Spectra-Source for only $330 more than the Celestron CG9.25.

The C9.25 was a truly wonderful telescope and would probably have been my primary telescope for many years. However, one day I found my self owning a Celestron CG11. While the C11 does not have the same quality optics as the C9.25, the extra aperture really comes in handy for astroimaging. I could not justify keeping both telescopes, thus the C9.25 and GM8 now have a very happy new owner. After eight months of using the C11, I am considering replacing it with another C9.25. Yes, the C9.25 is that good!



Back to the telescopes