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Canon 80D producing weird artifacts that appear after stacking

Canon EOS 80D Processing Stacking Deep Sky Artifacts
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Sami Sharafeddine avatar
Sami Sharafeddine avatar
I have a canon 80D, that is astro modified (UV/IR Cut filter is completely removed and replaced with clear glass), individual frames don't seem to much issues other than the random noise. But when images are calibrated, registered, and stacked, weird color artifacts start showing up in the final image, they also seem to be the same exact pattern too with just different colors!

andrea tasselli avatar
andrea tasselli avatar
Hot/dark pixels clusters in darks/biases can lead to those effects.
dkamen avatar
dkamen avatar
Sigma clipping should take care of them.
andrea tasselli avatar
andrea tasselli avatar
That very much depends on the strength of the artefact and the strength of the rejection threshold. I'd postulate that a wiser approach is to remove the affecting pattern "root and branch" from wherever is coming from, possibly by using a cosmetic correction approach (at least in PI).
Christian Großmann avatar
Christian Großmann avatar
I had the same effects in one of my images. I assume you dithered the subs? At least, it seems to work. Usually, hot pixels like this should be removed by the darks. If you use a dark library, then you may renew it. Hot pixels are small defects and they occur with the aging sensor. If the library is to old, it couldn't know about new hot pixels. But creating a new lib with a DSLR is no fun.

The suggested sigma clipping filter may help. At least it is worth a try.

CS

Christian
Concise
dkamen avatar
dkamen avatar
andrea tasselli:
That very much depends on the strength of the artefact and the strength of the rejection threshold. I'd postulate that a wiser approach is to remove the affecting pattern "root and branch" from wherever is coming from, possibly by using a cosmetic correction approach (at least in PI).

In my view what we have here is one hot red pixel and two hot green pixels that darks somehow didn't remove (or perhaps introduced). You can see the three patterns are identical so probably caused by dithering (which attenuates them somewhat). Also, lots of subs. Well that's what even the most naive clipping is for
Sami Sharafeddine avatar
Sami Sharafeddine avatar
Thanks for all the suggestions! I'm going to try running sigma clipping and play around with thresholds to get these artifacts removed, If unsuccessful I guess the only way is cosmetic correction.