I am starting narrowband imaging. I am using a 7 nm H-alpha filter (this one https://www.teleskop....php/info/p9231) and I am imaging with a QHY163M and a C8+fr.
I have tried imaging the Crescent nebula, but after stacking 30x4 min. subs (gain 150, chip at 0 C plus bias, flats and offsets from a green zone), the result looks a bit underwhelming... guiding was good, and there were no other issues during the session.
Here is the final image (stretched, 50% reduction for fitting CN). I have to say, the C8 is an old Ultima8, probably 30+ years old, and the coatings may not be the best ones around, but looking through the tube I cannot see any problem... is the Crescent nebula inherently dim, and am I expecting too much for 2h integration time? Or is there anything obvious I am missing?