Quote:
Originally Posted by Peter Ward
The extended halo around NGC253 is real and well documented, you have captured this very well. 
But.. sorry, I suspect your flat-fields need re-calibration.
There is vignetting and flux at 2 o'clock in the image you posted: likely this is an instrumentation artifact ( along with the bright corners from the vignetting) .
There is also an interesting s-bend looking feature at lower left!
Could be you have discovered a new neb..or might be an instrument artifact. 
Attached your posted image with the proverbial stretched out of it... |
Hey I was having a lend of you in my replies last night, you do put up a large target with your strange manipulations and wild accusations about my images sometimes
but on reflection Peter and given your use of inverse polynomials etc in your processing I would have thought you would know better
Grossly stretching the contrast of an already stretched image beyond reasonable levels with the
sole intention of revealing minor blemishes, will obviously then grossly exaggerate any tiny variation that may exist across the frame too and cover up the
real features like faint galactic cirrus. This of course will happen if you apply such meaningless heavy handed processing to just about
any image with such a high contrast stretch and will show tiny fractions of a % variations to be big black areas
. Try it on Martins latest Crab for example, same thing happens ie the left side of the image becomes all black while the right side is still light and there is a noticeable processing ring around the Crab too but these are
completely unnoticeable in the original (and beautiful) image.
Sigh...can't wait for your reply
Mike