Processing an Ha image the other day with my new ASI1600MM-C, I noticed a faint checkerboard pattern in the background. I have seen some discussion of it online, but nothing seemed conclusive. Any ideas how to handle it?
The attached ridiculously stretched processed stacked image shows the pattern clearly. It's not apparent in any individual sub as it's way below the noise level - which is already low. Not exactly sure at what level it is in the original data, since there's so much nonlinear stuff been done to this image. As it stands in the stretched version, the background is oscillating between say 12000 and 13000 ADU in that pattern.
Not sure if it's going to prove a problem in an image stretched more reasonably, but I think there are hints of it (bottom centre) in
this image on Astrobin.
Comments/advice appreciated.
Thanks,
Paul
PS This was gain 202 offset 50.
PPS Subs were dithered to try to address any such fixed pattern noise issues. And obviously biases, darks and flats used.
EDIT: Just confused myself completely now. That image is a stack of subs from two nights. One night I dithered more than the other, so looked at the two separate night's stacked individually to see which had the pattern more badly. Neither do!! And yet it's there in the stack of the two nights together - even without any processing. Visible with just a Histogram stretch in PixInsight on the output from Pixinsight's ImageIntegration tool. So is it some bizarre ImageIntegration effect on images from two different nights (with two different noise levels as the moon was much worse on the second set) rather than anything intrinsic to the camera's noise pattern?