Have a look at the halos around the bright stars in these 5 pics.
1. William Optics 110mm refractor (APO)
2. 6" Newtonian reflector.
3 Meade LX200.
4 Stellarvue refractor
5. 88" RC (University of Hawaii)
With the refractors, you might be tempted to say that is was chromatic aberration, but since the reflectors show a similar effect, it may not be CA. I tracked down a couple of interesting articles which may throw some light
on this issue. The essence of the matter is that they are probably due to internal reflections in the camera, that is, from the glass plate covering the imaging chip.
Have a look
here and
here
Geoff