Here's a screen shot from CCDInspector, a powerful program that I sometimes use to evaluate my images. This software does a nice job of quantifying certain characteristics of a series of CCD images, such as FWHM and contrast ratio, which makes it easy to identify the bad ones. Since most processing jobs involve combining multiple images, CCDInspector is a powerful tool for culling the best ones.
This particular image is the software's attempt to measure the curvature in my imaging train, as well as the collimation. Basically this helps me to see whether the camera is perhaps not orthoganal to the telescope lens, or whether the telescope is out of collimation. Ideally, you would want a perfectly flat image, but that is virtually impossible to achieve. A system with a lot of curvature will exhibit noticeable distortion in the images. I'm very pleased that this particular system, my William Optics Zenithstar 105mm with a 0.8 focal reducer/field flattener, provides a reasonably flat result. For a relatively inexpensive system, it has done quite well for me. Of course I dream of something better and perhaps someday will upgrade, but it's nice to know that the current setup is not way out of whack.
I used my ZS105 on Sunday night at an observing session over at Dean's house. I spent some time fiddling with software configurations so don't have a lot of data, but I'm working on processing it and should be able to post it soon.
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