Quote:
Originally Posted by Peter Ward
Not saying you haven't...but if it didn't dark subtract out...it was not longer a class one and good reason for a warranty claim.
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No, it was brought to the attention of SBIG and they said it was normal and not a column defect and merely a hot pixel which does not cause it to not be a Class 1. You'll see these lines also on the 16803 chips as well although these chips are quite noisefree at -10C.
From memory a class 1 has no column defects and hot pixel groups are less than a certain number.
Without exception ( I've tested hundreds of cameras) I have traced this to less than perfect dark frames....sure, lowering the temperature made the effect less obvious, but nailing the dark frames extinguished the problem.[/quote]
Yes you would be right there. I wondered what that difference was sometimes. Perhaps the bias frame reduction on the flats caused it.
It sometimes seemed a bit random. My darks were quite good. Oh well a bit of a mystery, sometimes it went and others it did not. Perhaps using a bias puts it back in there as the dark subtracts it and then it is gone and then if you use a bias in your flats you put it back in the flat and it comes through again? Perhaps better not to use a bias frame in this instance when making your flats.
Greg.