CPC 11

Here are my inexpert comments on the scope I used on 04Sept2010 at New Mexico Skies.

The Celestron CPC 11 Schmidt-Cassegrain is a wonderful telescope! Mounted on a concrete pier, it is rock solid. It was a breezy and gusty night when I was using it, and while the wind played with it a bit, the scope recovered very quickly.

The computer controller was easy to learn and easy to use. I am used to the Meade version, which is similar, so it took a little unlearning there, but it wasn't long before I felt very comfortable with the controls. The scope is permanently mounted, but Lynn led me through the alignment process, which was also very easy. Once aligned, the GOTO function was spot on most of the night. It started to miss a little bit late, but with the addition of another alignment star, which was also very easy, it regained its earlier spot-on-ness. The tracking was also excellent. I suspect it would be very adequate to basic astrophotography, although I can't really speak to that. For my purposes, though, it was perfect. There was no slippage in either RA or Dec, so objects stayed centered with no outside help. This is a remarkable difference for someone who doesn't have a tracking scope, let me tell you! Also, the tracking was essentially silent. No humming or clicking or anything to let you know it was doing its job.

Again, I am no expert on optics, but the views were bright, clear, and sharp, once I learned how to focus a Schmidt-Cass. It has a knob for moving the primary mirror and a two-speed focuser for the eyepiece. I'm used to one knob. Anyway, images were in focus pretty much across the entire field of view, right to the edges.

====Geek Break! ====================================

The CPC 11 is an f/10, for those who know what that is. For those who don't, that means the focal length (basically, how far it is from is from where light first enters the scope to the eyepiece) is ten times the aperture (the diameter of the primary mirror or lens). So, if I did the math right, the 11" aperture is basically 280 mm, and the focal length is then 2800 mm. To find the magnification of a particular eyepiece, divide the scope focal length by the eyepiece focal length. I was using the following eyepieces, provided by NMS, with respective magnifications.

• 40 mm = 70 X
• 38 mm = 73.7 X
• 30 mm = 93.3 X
• 20 mm = 140 X
• 15 mm = 186.7 X

====End Geek Break! ====================================

The optical performance was equally good as far as I could tell at all magnifications.

All in all the CPC 11 made for a great night of observing! The only complaint I have is that I don't have one.