Thank you for your reply! I have not used any filter with this setup (I use an l-enhance clip-in with my EOS which I usually use for deepsky). In another forum, somebody told me that an UV/IR-cut will make a huge difference in particular with the 485 since its sensitivity for anything above 800nm is quite high. I will try that next after some adapter arrives (putting an 1.25inch filter into a standard M42 train is a huge problem if you don't want to use an entire filterwheel). For planetary imaging I do not see any such artefacts. In fact, I am loving the cam for recording moon or jupiter..absolutely crisp and amazing resolution with the 2.9um pixelsize.
Is your attached picture recorded with an IR/UV-cut? What is the exposure/gain? I saw that unity for the 485 is somewhere between 50-80 (measured with SharpCap). I see that even in your picture there are slight halos around the stars?
