Flats nightmare

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admin
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Re: Flats nightmare

#11

Post by admin »

Hi,

glad to hear that you are back on track - hope that you get some clear skies to put all of this into practice soon!

cheers,

Robin
m32guy
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Joined: Sat Sep 21, 2019 9:11 pm

Re: Flats nightmare

#12

Post by m32guy »

Just found this thread and can't tell you how much it's helped. I've been going nuts trying to get reliable flats for my LRGB images (shot at 121 gain) and yet have had no problems with my Narrowband flats shot a 300 gain. Now I think I know why. Next LRGB run I'm going to try and shoot my flats just under unity at 119 and see what happens.

Quick question. So if I shoot my flats and darkflats at 119 gain, should I shoot my darks at 121 to perfectly match lights? Or should dark frames be shot at gain 119 too?

Thanks, Steve
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Re: Flats nightmare

#13

Post by admin »

Hi,

if your flats are giving you trouble at 121 gain then I would avoid that value entirely for imaging (lights, flats, darks) - the fact that the flats are not working indicates sensor non-linearity due to the not saturating issue. I'd either go with 119 or less, or about 180+ to avoid the problem range.

Whatever you choose, the darks do need to be taken at the same gain/offset as the light frames, but the flats can be at different gain.

cheers,

Robin
m32guy
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Re: Flats nightmare

#14

Post by m32guy »

Thanks, Robin. I will avoid that range for now. Quick question then. I use the Brain a lot for getting my exposures right. What's an easy way to figure out the correct exposure length for 190 gain? Do I set the brain to Unity and adjust off of that?
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Re: Flats nightmare

#15

Post by admin »

Hi,

you can click on the green curve in the graph at the bottom of the brain window - click at the gain=190 point and it will read off the suggested exposure for that gain.

You will have to enter the exposure manually mind you...

cheers,

Robin
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