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Old 20-02-2014, 03:44 AM
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skysurfer
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Weird gradients after stacking with DSS

Yesterday night I shot the NGC 3372 area with a 85mm f/1.8 squeezed to f/2.5. I used an unmodded Canon 6d and took 30 frames of 10 seconds each. Light pollution of 30km away Cape Town did not allow to expose longer on 6400 asa. So I took 30 frames.
The result appeared weird as the bottom of the image has some yellow discoloration while the original; cr2 frames did not have this.
Does anybody know what might cause the gradient ?
30 frames, 4 darks, 6 flats stacked with Deepskystacker 3.33.

http://pix.skysurfer.eu/ngc3372-30x10sec.jpg
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  #2  
Old 20-02-2014, 07:00 AM
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lazjen (Chris)
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Have you checked your flats and darks to ensure they're not introducing the problem? You could try stacking various combinations (no flats and/or no darks) to see if the gradient remains.
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Old 20-02-2014, 01:46 PM
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ZeroID (Brent)
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Amp glow on the sensor ? 6400 ISO is pretty sensitive to ambient noise and factors.
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Old 20-02-2014, 02:01 PM
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Looks like you used no flats.

Always do many different stacks with DSS e.g.

sometimes on these wide field shots if you
have "remove hot pixels " ticked it will make a real mess of the result
by removing every faint star.
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