Author Topic: MasterBIAS v SuperBias calibrating for MasterDark - Doesn't seem right to me  (Read 340 times)

Offline STAstro

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Guys

I am a bit lost here now, I have followed the LightVortex steps on creating a SuperBIAS from 999 BIAS frames, however I am a little concerned about the results, the first two images show the MasterBIAS on the left and the SuperBIAS on the right, the 2nd image shows the resulting MasterDark after calibrating all the dark frames against the MasterBIAS (Left) and SuperBIAS (Right), all images have had an STF applied.

The third image is a MasterDark with no BIAS deducted which to me looks a lot more "Normal"

Why do my MasterDarks look so bad when the Master/SuperBIAS has been deducted?  Does anyone have an example of their MasterDark when BIAS has been subtracted during the calibration of the darks?

Offline pfile

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there's no point in using a master bias if you have amp glow like that. you can't scale the dark because of it. so just use dark subs that exactly match the duration of the lights, make a master dark using those dark subs, and subtract it from the lights to fully bias/dark calibrate the lights. you need to uncheck "optimize" in the dark area of the imagecalibration process to make sure there's no scaling.

rob

Offline STAstro

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Hi Rob

Fancy seeing you here :)

Surely I must subtract the BIAS from the Flats though right?

Regards
Simon

Offline pfile

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well, assuming the flats suffer from the same amp glow, you should probably use flat darks for the flats...

or maybe they don't have such bad amp glow because the flats are short enough? in that case you could use a master bias to calibrate the flats, yes.

rob

Offline STAstro

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Thanks Rob

My Flat frames are the following exposures

L - 0.08s
R - 0.86s
G - 0.32s
B - 0.14s
Ha - 2.90s
OIII - 0.96s
SII - 4.15s

I'll take some dark flats anyway as I am just building my new library due to Gain/Offset change recommendation by QHYCCD, I'll inspect the 4.15s frames and see if the amp glow is evident, but since I am doing dark flats anyway...meh :)