Hi Paul,
I saw the gradient but was not worried about it.
When you try to get rid of it it's too easy to remove faint galaxies.
I looked for other details.
You have a lot of details of the giant elliptical NGC 1399.
see link:
http://cseligman.com/text/atlas/ngc13a.htm#1399
Your choice of framing is amazing.
It's so great to get all that in one frame.