My C-11

Back in 1989 I acquired a used Celestron 11, inscribed on the mirror I found the manufacturing date: 11 May 1988. I sold this C-11 in 1995. In 2005 I had the chance to buy this C-11 back from the person I sold it to. I know this is a good instrument, so I was glad to have it back. Here are a few pictures.

The C-11 is held by two sturdy Parallax rings which are mounted on the Alt 7AD dovetail. A Casady/losmandy dovetail holder on the upper side of the rings is used to host other scopes piggy-back onto the C-11. The shiny part on the OTA is isolation foil, believed to slow down irradiation and tube currents. As the telescope is in an unheated observatory, it comes to ambient temperature in a short time.

Nope, not a Fastar C-11 this one! The controlbox to the left is a DewBuster which a controls a Kendrick dew-remover strap.

The back of this 1988 vintage C-11 is different than current day C-11s which are virtually flat on the backsideof the mirror cell. The focuser is a Clement Compliant Focuser, large and ugly but it works well.

Startesting.

Images are made inside and outside focus; in a good refractor these images would be almost identical, not so in a compound telescope. The aspect is similar however, showing a slight decollimation and of course seeing effects, the seeing was only 2 to 3 on the pickering scale when these images were made.

Another test one can do is a Ronchi test, this is more easy in visual use than with a camera -especially on a real star. The Ronchi bands should be straight, contrasty and evenly spaced.

C-11 Surgery.

Commercial SCT's from Meade and Celestron are quite easy to operate on and all are similar. These images were made in November 2005 when I opened the C-11 to apply new grease to the baffle tube. I took the opportunity to make some measurements of different components.