All individual flats need to be bias calibrated when you create the masterflat. So all flats need to have a b in the frame column before you create the masterflat. I’ll be happy to demonstrate it if it’s needed? Mabula
No, you don’t need to do that Mabula, i will just wait for the manual before i will use APP for DSLR images. At This point in time APP just swallows everything i throw at it and stacks without any warning or guideline.