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Old 31-07-2014, 09:20 PM
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Shiraz (Ray)
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Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,822
just tested an alternative method for flat fielding that seems to get around the introduced noise problem. PixInsight has a background estimation algorithm (DBE) that generates a smooth surface representing the sky background. I extracted such a background from a single starfield sub and then applied it as the master flat in the standard calibration process for a complete batch of subs. Worked fine to clear up some minor vignetting and the resultant calibrated data is flat to better than 1% across the frame. And of course there is no dark noise, no read noise, no shot noise and only a little residual bias subtraction noise in this type of flat.

Would not work on dust bunnies, but can possibly provide high quality control of vignetting without introducing much flat noise at all. Of course it will not remove fixed pattern noise, but dithering can take care of that.

Be interested in opinions on this technique - I have only tried it one dataset, but it worked OK on both the lum and RGB data..

Last edited by Shiraz; 31-07-2014 at 09:43 PM.
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