Colour Calibration

[Mariner10]

Hi,
I have an image of the Rosette Nebula that is quite large and essentially full or red nebula and stars with very few dark areas.
When I want to do colour calibration and want to make the background darker I'm struggling to find an area dark enough for the preview box and the end result is quite ordinary.
I was wondering if there is anything that I can do to rectify this, if there's another process that will achieve the same result of darkening the background.
Thanks.

Steve.

[jkmorse]

If you have captured the heart of the Rosette, you should have adequate background to work with.  Just zoom in and select an area without stars.  If you need to combine several to get enough material, then simply use the preview combine feature.

Good luck,

Jim