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You should be happy Erik. A great first run at Ha imaging. Narrowband work is ideal for nights the pesky moon is about. Starting to pick out the faint structures of the area. You are correct in that as the Ha filter has a significantly small light bandpass than a luminance filter, you need to counteract this with longer sub exposures. I've personally had great results with 15min subs on fast optical systems say F/5 and below. Slower will require longer obviously. Generally longer subs are better to pick up the faint signal and will make your life easier when it comes to processing as low signal and noise go hand in hand. Maximise the signal where possible. When combining narrowband subs, many use 'sum' (as opposed to mean or average) to obtain as much signal as possible. Sum will wreck havoc on bright stars (saturate them) so you may need to layer the result to get the desired effect you're after. You're on the right track. Keep at it.
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