Strange Artifact I've Never Seen Before

Acquisition Deep Sky M106 Artifacts Messier Objects
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Jerry Gerber avatar
Jerry Gerber avatar
While processing M106 this afternoon I came across this weirdness:



Does anyone know what might have caused this?   I was able to process it out, but it's still concerning to not know what might be causing it.

Thanks,
Jerry
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Oskari Nikkinen avatar
Oskari Nikkinen avatar
Need more details.

What processing software, what calibration worfklow, is this an autostretched image with just an STF applied?

Without details, i have seen something like this but not exactly like this, with a 16-bit stack produced with under exposed subs.
Jerry Gerber avatar
Jerry Gerber avatar
Hello Oskari,

Thanks for replying!

Pixinsight for calibration, pre-processing, image registration and integration.   I have played around with the histogram transformation and can see the artifact in the stretched image, but barely.  It's when I import the TIFF file into ACD Photo Studio Ultimate (my photo editing program of choice) and start applying different versions of LIGHT EQ (it's like an audio EQ but for light frequencies) that I really begin to notice it.   I've managed to remove the artifacts in my final (maybe) image but I'm still perplexed as to what caused them in the first place.  The artifacts are definitely not on the integrated unstretched image.  




Attempt to create finished image:

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Oskari Nikkinen avatar
Oskari Nikkinen avatar
Did you export as 16-bit? Or is ACD photo studio (unfamiliar with this one) doing some sort of data conversion to reduce the precision to 16-bit on its own?

My bet is this is some sort of 32-bit to 16-bit gremlin.

What you should do is do all linear processing in Pixinsight, which means gradient removal, colour calibration and initial stretch. After you have stretched the data to a point where 32-bit is no longer necessary you can convert to 16-bit to further work on the stack with any software.
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Jerry Gerber avatar
Jerry Gerber avatar
I exported as 16 bit, as I always do as my photo editing program doesn't read 32-bit files.

Strange thing is that I tried exporting a second time the 32-bit XISF file in PI to my photo editing software in 16-bit and the artifacts disappeared…
Weird..
Brian Puhl avatar
Brian Puhl avatar
Enable 24 bit interpolation in pix.   Should fix it.

Jerry Gerber avatar
Jerry Gerber avatar
Brian Puhl:
Enable 24 bit interpolation in pix.   Should fix it.


Thanks Brian, I'll try that.  I've been processing images the same, or similar ways for a while now, I wonder what's different about this one, I've never seen this before.  I started over with the unstretched integrated image and repeated the same processes, only this time the artifact didn't show up..
Brian Puhl avatar
Brian Puhl avatar
Jerry Gerber:
Brian Puhl:
Enable 24 bit interpolation in pix.   Should fix it.


Thanks Brian, I'll try that.  I've been processing images the same, or similar ways for a while now, I wonder what's different about this one, I've never seen this before.  I started over with the unstretched integrated image and repeated the same processes, only this time the artifact didn't show up..



This article explains why it happens pretty well for you. 

https://pixinsight.com/tutorials/24-bit-stf/
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