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Old 01-08-2014, 09:58 PM
SpaceNoob (Chris)
Atlas Observatory

SpaceNoob is offline
 
Join Date: May 2012
Location: Canberra
Posts: 268
Quote:
Originally Posted by Shiraz View Post
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..
The DBE tool works quite well, ABE too. I did not bother with flats when using the FSQ106 @f5, using the CDK though I first started to notice the impact of dust bunnies.... DBE did reduce these slightly, but not enough to justify not using flats at longer focal lengths. I also found it useful for battling gradients from street lights and other additive sources via subtraction.
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