I used an AT8RC last spring/summer with an ASI294mm and RGBL Baader filters. I am away from home and just trying to process some images I took over that period. I noticed that some images have rainbow stars. I thought that maybe my scope was out of collimation, even though it is stored in my observatory and doesn't move. Today, I just noticed that I had an image taken after those with rainbow stars and it looks good.
I have really thought about the possible causes and remembered that I imaged a few times when there was a smoke warning, although I didn't notice any. Is it possible that faint smoke could act like atmospheric dispersion and cause this? Did anyone else notice this effect? Any other ideas?