I shoot for ~3/4 to the right of the histogram. I have gone down as low as 50% histogram. Because the stacking results in a 16-bit image file, the brightness can easily be adjusted in post processing.

Astroimager Adam Block has produced three image-processing tutorials on 4-gigabyte USB flash drives. Each includes between 100 and 161 minutes of instructional video as well as the raw data for ...