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Pseudoflat question for full disk images

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#1 edremy

edremy

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Posted 12 August 2017 - 10:04 PM

For some odd reason, I plan to take a lot of full disk images Monday after next.  I'm having some issues getting with even brightness across the disk though.  (Lunt 50, ASI120mm camera.  I think the brightness issues are probably due to some sag in the focuser which could be fixed with $$$ in the future, but not in time)   Here's a simple surface image before any attempts to correct this

 

fulldisk-im-half.png

 

I've tried creating a pseudoflat for this by taking the initial image and running a Gaussian blur on it.  I've constrained the blur to the disk area since otherwise you get ugly edge effects.  This looks good at first

 

fulldisk-psf-up-half.png

 

But it still has some edge effects- note the brightening on the upper right.  This ends up looking quite ugly when merged into a prom image- you get a black ring that doesn't look natural at all.  I've tried fiddling with the size of the blurred image, making it very slightly larger and smaller to see if I can find a point where the pseudoflat won't do that, but I'm not having any luck.  Anyone here with a lot more experience know a trick that can work?  (Sorry for the size, but it's hard to see on the shrunken versions)  Thanks in advance for any help.

 

fulldisk-psflat2-imppg-merge.png

 




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