I've been working on properly collimating my Hyperstar 4 for EdgeHD 8. I've been getting what appear to be good photos and getting close to collimated using CCDInspector, but one thing seems a sticking point.
I've gotten the aspect into the single digits, collimation below 5 arc/sec on a pretty good star field, and tilt is ~ 1 arc sec or lower on both axes.
However, despite using autofocus, and regardless of exposure length, I am getting a reported FWHM of 8 arc-sec in both CCDInspector and Pixinsight subframe selector, whereas I would have expected around 4 arc-sec fwhm or lower given my skies and typical guiding results at f/7. Binning is 1x1.
I've been banging my head against this for a bit, could use some extra eyes on it! The 2x of it makes me suspicious, but I haven't identified any data entry issues. Focus seems to be working, and the images are coming out okay -- it's just the FWHM being so high would seem to indicate I can do better. I've tried short exposures as well with similar results.
My setup is the EdgeHD 8, ASI 2600MC, Hyperstar, GM11, gain 0, offset 50, binning 1x1, SGP auto focus. It should be at 400mm focal length. Camera pixel size is 3.76nm, RGGB.