Saturday, October 8, 2016

Bright, vertical columns in Darks

I took new darks and also bias frames, and they show bright vertical columns:

Master Bias (1000 frames)
10 min Master Dark (51 frames)
But these don't show up in the flats or lights:
Master Flat (20 frames)
10 min Light Frame

And when I know calibrate the light frames, they show a dark column in the place where the bright column was in the master dark/bias:
Calibrated Light frame
I retook my master frames (bias, darks, flats), calibrated with Pixinsight or CCDStack - always with the same result ...

--- Update ---

I asked Richard, Tim, Jim and Richard about it. Apparently this is a rare but known problem with KAI/KAF sensors. Tim measured the pedestals and said that I need to add 24 DN to my lights in column 1285. With that, I get this as my calibrated light frame:
Calibrated Light frame with correction in column 1285
No more dark column on the left!!! Now I have to figure out the pedestal in the other column and then an efficient way to apply these corrections to my light frames.