Now that I seem to have control over most of the needed functionality, I turn to image quality.
Only one object has been imaged so far, Albireo or β Cyg. It was taken on a poor night but during the only clear spell so far available. Bear in mind that thin haze may have been present. The image shown is the green channel of the 40s stacked image. β Cyg B shows a very obvious ring around it, measured at a radius of 14 arcsec from the center of the stellar image. Other fainter stars show similar rings at 11-14 arcseconds radius. The radius Airy disk of a 50mm aperture in green light is 2.4 arcsec (and pretty much the same for FWHM) and the first bright diffraction ring should be at 5.4 arcsec assuming I calculated correctly. Much less than 14 arcsec anyway. The image scale is 2.37 arcsec/pix according to astronomy.net; this is a good match to the Airy disk size.
Any ideas what may be causing this? Stray reflections is one possibility that comes to mind, as is rather bad spherical aberration.
I will take more images on properly clear nights to see whether the effect is reproducible but I would be interested to learn whether other Seestar users experience the same effects. If not, perhaps it should be fixed / or exchanged under warranty.
Here’s the image which shows the ring.
