Hello! I'm curious about the data that I obtain from what I would call "bad" images.
I use MPO Connections for automated image acquisition. At times during a night's run, the autofocus fails for a particular variable, and I have donut images for those variables. Sometimes, the images are oval or mildly trailed even though the focus would seem to be otherwise fine if the image were not trailed.
I believe I've read that as a star's image is defocused, the pixel light distribution departs from a Gaussian distribution. When I analyze these types images with enlarged apertures, the magnitudes appear to match that which would be expected in the historical light curve. And the error range of the measurements still appears good.
I'm wondering if it might be worthwhile/educational to check my set-up to see how star magnitudes might vary with the amount of defocus from an evening's optimum FWHM as well as how the amount of star trailing might affect star magnitude. I realize that there is discussion about how aperture size should be set to reflect FWHM of an image, so I would need to try to control for such variables.
I would think this type of analysis has been done before. Could folks suggest sources of information or papers that might have looked at these types of issues for "bad" images? Thank you and best regards.