as we are lucky to have a friend on site right now in Namibia, a few tests have been done. Among them, we added some holding rings to our QHY filter wheel. Do not ask me how the guys at QHY came to the idea that this should be the way to design a filter wheel (note: faces the scope):
Of course this could potentially create any combination of reflections. So some friends did a 3D print of small black rings that would gently hold the filters in place, creating a nice round border:
This of course means that all flats taken before 6th january 2022 are to be considered "old"... Will collect new ones asap.