One of the real disadvantages of an urban setting is vignetting caused by stray light and light pollution and/or smog in the sky, causing "skyglow" and saturating our images prematurely..
Recently I downloaded the free trial of Gradient Exterminator and applied it to many of my Astrophotos. It's very easy to use and made instant improvements to almost every image I used it on. I've since purchased this photoshop add-on.
I am very happy with it. Thoughts?