Sharpcap has a feature called Smart Histograms. It allows you to point your scope/camera at part of the sky with few stars/objects and get an analysis of the light pollution and shooting conditions. Then, it suggests an optimized gain setting (you can choose Unity Gain as a target) and an exposure length to use. Additionally, it allows you to request an hour worth of camera time and it will tell you whether to do 60 second exposures with 60 images or 120 second exposures with 30 images. Maybe the ideal method for ASIAir Pro would be to auto-slew to your object, use a selection tool to draw areas in the photo that do not contain nebulosity and has fewer stars, and then it calculates the exposure time and number of exposures. While you are at it, maybe allow for easy override of the calculated exposure to something that matches your existing dark library exposure time(s).
