[Dennis]

Hello,

I have just been reading the manual for CCDSoft which is the camera control and image processing software provided by SBIG for their ccd cameras, and I found an interesting function called “3-D Surface Plot” under the “Research menu”. This command displays a three-dimensional graph of an image.

So, I grabbed a few old images and cropped a single star to generate a 3-D surface plot for that single star, then I viewed the plot from above and lo and behold, I think it tells a story about collimation. The images I chose were made with exposures of between 60 and 90 secs with my ST7, which may be too long? Anyhow, here are the results for:

Celestron C9.25 at F6.3 (using reducer/corrector)
Celestron C9.25 at F10
Vixen 102mm f9 refractor

It shows the Vixen refractor is nicely collimated whereas collimation appears off with the C9.25. Next time I am out (=when Brisbane gets some clear skies) I may try collimating using a star with say, 5 sec exposures.

Cheers

Dennis