Result of test using 8 seconds at 350 gain only 32 frames...and focused using mask.
First image uncropped but will suffer from weight loss.
the second is a cropped section that may show how the large one presents.
that is 4.2 minutes exposure
no doubt I could have used less gain ....is it fast ...yes it certainly seems to be... I may try doing a narrow band in less than an hour for a bit of fun and to fit in the time frame usually available
alex