Is this a flat problem

Discussion of using SharpCap for Deep Sky Imaging
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psy1280
Posts: 208
Joined: Wed Oct 24, 2018 4:52 pm

Is this a flat problem

#1

Post by psy1280 »

I'm trying to work around my difficulties using the ZWO294 (well known for it's difficulty capturing flats). Although I applied a flat to these images, I'm not sure if this is exclusively a flat issue. I'm in a 7-8 light pollution area (using L-Pro LP filter). The white balance seems correct looking at the Whirlpool and according to the histogram in LiveStacking. I'm going to keep trying to figure out how to get the best flats with the 294, but I'm just not sure if that my only problem.

SCT 8" Celestron f/6 focal reducer
Exposure 60 seconds
Gain 170
Brightness 8
Temp -14.8
No Dark or Dark Flat
Raw 16
L-pro light pollution filter

Thank you all,
Joe
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Re: Is this a flat problem

#2

Post by admin »

Hi Joe,

looks like your flat has over-corrected (assuming that it was trying to remove vignetting). This can happen if you do not use darks along with the flat (basically if you do not use darks then the flat ends up correcting the part of the signal that the dark removes, which you don't want as it's not due to light). You should also use dark flats or bias substaction when creating the flats or you can end up with the opposite effect.

Robin
psy1280
Posts: 208
Joined: Wed Oct 24, 2018 4:52 pm

Re: Is this a flat problem

#3

Post by psy1280 »

Much thanks Robin, fantastic advice! Can't wait to try it out.
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