Tag Archives: Celestron

Trying out a used Celestron C11

In January 2014, I made it another step closer to becoming one of those amateur astronomers who has x number of telescopes…that his wife knows about. Celestron marketed the C11 Ultima, a 280mm f/10 telescope, in the mid-1990s, and I picked one up second hand at Hands on Optics for a very reasonable price. And by the way, I recommend that anyone interested in a telescope or binoculars stop in and see Gary Hand, because you never know what you might find there. The telescope had been installed in an observatory, and as a result it was somewhat exposed to the elements for a number of years and it needed some work. I cleaned the exterior surface with a premium car polish, and it looks as good a new with the exception of some minor scratches. The V-style dovetail plate was loose because the attachment screws were too long, and therefore would not tighten. I was able to easily repair this. In the short term, I wanted access to a larger SCT reflector to gain experience with a longer focal length and bigger aperture instrument, and to learn how to collimate a reflector. I have been able to take it out just once, and I can see that I have a lot to learn. In the longer term, there may be some potential for more work on the the telescope. I doubt that the mirrors have ever been resurfaced, so that is a possibility. The multicoating on the corrector plate glass is in pretty bad shape. I hear that this is an expensive repair, so I might just have to live with it. And finally, I may install a cooling fan, which will help the telescope reach an equilibrium temperature with the outside air faster. The telescope weighs 22 lbs. Since this approaches the maximum capacity of my mount, I am already thinking about my next major purchase.

© James R. Johnson, 2014.