I shared over on CN an unstretched .tiff that was the output from pre-processing and stacking using Siril. One of the members there freaked out about the histogram being ‘quantized’. So I went back to a single original .fits file, opened it in Siril, and applied auto histogram stretch without doing anything else and got basically the same thing:
This is from a QHY183C, captured using Ekos. I have checked the INDI driver settings and see nothing other than the expected 16-bit settings:
I can talk myself into most any conclusion (in general, not just here). For example, the QHY183C is a 12-bit camera that upscales to 16-bit output by multiplying each pixel by 16. So in fact, there should only be a value for 1/16 of the 64k possibilities and this is pretty much expected, right? On the other hand, he seemed pretty freaked out by it.
So - if this is normal, I shall stop worrying. If it is abnormal, I presume the issue is on the Ekos side and will go ask in that forum.