Quote:
Originally Posted by allan gould
where in nebulosity can I determine the ADU count for a particular exposure. I was trying to use the histogram but it really didn't give me the information I needed.
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haaa.... I got caught on that one too. Beware of the bayer matrix... it's everywhere
Seriously don't look at the histogram. Take your flat in preview mode then center it and rollover your mouse in the brightest part of your flat (usually the center) and look at the pixel ADU value in Nebulosity status bar bottom right. Now here comes the tricky part. I told you by trial and error with my QHY8 I go for a max of 9000-10000 ADU right? (might experiment with your QHY*, may need different levels) Well, the ADU values are radically different in the 1xR, 2xG or 1xB pixels. You may get only 2000ADU or so in the blue when the red is already well over 10000ADU. So I check the flat level in the brightest pixel of the bayer matrix regardless of the color and base my exposure time on this. I got caught the first time by doing Ha that falls only in the red, then checked the levels on an area of pixels rather than individual so although my average ADU was well within 9000 ADU I still had pixels well over 30000 ADU in the reds.
Talk about inverted vignetting as soon as I debayered
