Light pollution causing gradients is a major problem with the sky at my observatory site i.e. home in the outer suburbs (16 km) from Melbourne.
PixInsight has a module called Dynamic Background Elimination or DBE which works very well to get rid of even bad gradients. My data still had remnants of these gradients especially in the green channel.
Greg Bradley put me on to HLVG here
http://www.deepskycolors.com/archivo...sta-Green.html
This is quite good minimising green noise in RGB data.
An example. NGC 2070 at 1.5 times native pixel size in RGB 20MB
http://d1355990.i49.quadrahosting.co...0_RGB_HLVG.jpg
And again RGB plus NB 20MB
http://d1355990.i49.quadrahosting.co...GB_HLVG+NB.jpg
Bert