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Old 17-05-2011, 12:14 PM
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troypiggo (Troy)
Bust Duster

troypiggo is offline
 
Join Date: Nov 2008
Location: Brisbane, Australia
Posts: 4,846
captured FITS not saturated, apply flats saturated!

Capturing and calibrating images from my QSI583 with Nebulosity. The captured light frames have a max pixel value of 64000, which I assume is not saturated as it's less than 65535.

It seems a very nice, round number that 64000 and it's consistent among all light frames. Could be stars, or since this image is uncalibrated, it could be noise in the form of hot pixels I suppose.

When I apply darks to it, the max value drops to, say, 63636. This makes sense as darks are subtracted.

Now if I apply my flats to it, this is where I'm puzzled. I have an image that I think is unsaturated. I've ensured my flats have their histogram around 1/3 to 1/2 of max, and there's no blackpoints or whitepoints reached in them. Flats are divided into the light frames. After this process, somehow my calibrated image has a max pixel value of 65535 and a min of 0! I've tried variations with blurring the flats in case there's hot pixels or black pixels in there, same result though.

Anyone know/understand what's going on here? Do you reckon it's Nebulosity specific or is it common/normal? Am I worrying over nothing?
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