Here's a cutout from a sequence I did last night on NGC5128. The CCD was an ASI533MC but I have encountered the same thing with other CCDs.
It is the repeated patterns of coloured dots, red, blue and green. The pattern of the dots is the same whatever their colour.
This was a DSS stack of 19x5 minute subs and roughly procesed with PS5. When taken (using ASiair Plus), I was using dithering.
Before posing this, I decided to process the same images using APP. Interestingly, I cannot find any trace of these artifacts in the APP image sothe answer lies somewhere in the belly of DSS.
