HI - I am about 30 miles from London, so the skies are not that dark. For this I had a 10" f/8 GSO RCT, with a QSI683, fitted with Astrodon filters. I use a 5nm Ha and a 3nm O3. I had 25 subs of 20 mins for the narrowband. I also took extensive LRGB but when I processed this in PixInsight, using the SHO-AIP script - they did not really figure much in the blend. In fact, I really just used the LRGB to make the star color natural. The Ha was assigned to red and the O3 was blended across G and B.
I discovered that my extensive luminance did not pick out the details very well, so I separately processed the NB, with masked stretch, local histogram equalization and a bit of multiscale median transform to bring out the detail. Only then did I combine them. I learned a lot and it will be a written up as a practical assignment in the next book.
On screen here, the background looks a bit noisy - but not on my original file, I will have to take a look at that.
Chris Woodhouse