After weeks of cloudy skies it finally cleared up and I was able to get in two nights of shooting. Looking at the results, a bit over 50% of the images had to be discarded due to some type of “jitter” in the stars. The attached screen shots (a portion of a 100% zoom) shows the issue: The stars appear to have either a tail or one or two dots off to the side. A bit less than half of the images are OK, but the rest show this problem; some even worse. It’s almost as if the camera shutter opened while the mount was settling, or the mount moved a little bit during the 3 minute exposure.
I had no problems at all like this on earlier shoots, but just before this one I updated both SGP and PHD2 to the latest version. Given that this problem occurred on two nights and only started after updating both programs, it makes me a little suspicious (and I’m leaning towards PHD2 as the culprit). The log file (Dropbox link) does show PHD2 having some issues after dithering, but I’m not familiar enough with the sequence log to know if this is an issue or normal behavior.
Any ideas what might be causing this problem? I think there may be a few hours of clear skies tonight before the clouds roll in, so I’ll try some shots with the older version of PHD2 to see if the issue goes away.
Cropped screen shot @ 100%:
