Hi, Chris,
I guess it depends on the camera you're using and its well depth.
I know with my STL-11000M on the FSQ-106N that I can expose for ten minutes without loss of star colour. Mind you, I've been binning 2x2 and exposing for a maximum of 5 minutes per colour.
I think you'll find the concensus is that, perhaps you expose for a quarter of the duration as your luminance to regain star colours again, and, then add them back in with a simple luminance mask limited to the stars.
Cheers.
H
|