I am revisiting some of my astrophotos to clean them up for publishing. In many cases it’s becoming obvious that my stars are not as sharp as they should be. I struggle trying to determine whether the issue is focus or guiding. I always focus using a live 8-bit video stream and autofocus to yield the smallest stars. When I look at my photos later I notice that the FWHM values vary from night to night and yet, in comparison, my guiding is fairly consistent. If FWHM varied with guiding…