Wayne,
NB images often require a different approach on color balance.
A couple of things you can try. One that I particularly like is after stretching to create a star mask to protect the stars, then use the Hue function in Curves Transformation (its the button labeled with H towards the right). Depending on the curve you create, and it may take a couple of iterations, you can do some nice color adjustments, though that is a bit of a blunt force approach.
The second way involves adjusting the color mixes when you combine the images. I am not sure what you used to combine your channels but one method that gives you complete freedom to tweak the mix is by using PixelMath in stead of ChannelCombination. Its actually an easy process, once you get it set up initially. To use it, open Pixel math, clear anything that may be written, then click on expression editor. Then for each color, simply insert your images (easiest by using the "image" tab on the right). So if you have Ha as red, just drop the Ha image in the Red column. For Green, assuming you are using a mix of Ha and OIII, then put in both images in the format [Ha image]*0.5 + [OIII image]*0.5. Do the same for Blue, though that will likely just be OIII. Now accept the expressions to get back to the main PixelMath screen from the beginning. Make sure that you open the bottom tab and check create new image and that it should be RGB. Now you can play to your heart's content, making adjustments to the percentage contributed by each of the individual colors, so long as they add up to 1 (i.e, you can change the 0.5 and 0.5 to 0.2 and 0.8, for example). In fact, you can even go over 1 if it doesn't blow out that color.
A third way is with the SHO-AIP Script. There, again after stretching, you do much the same thing with mixing that you can do with PixelMath.
Good luck.
Jim
