Here is my attempt at a two-panel mosaic of Cepheus area.
I did an experiment trying to go deeper in strongly light polluted sky conditions by using long exposure (over 15 hours per panel), narrowband filters (down to 3nm) and very fast optics (f/2).
The results are interesting. I can certainly pick up quite faint Ha/SII signal.
However, shooting with a small aperture (70mm) I could not get enough signal-to-noise on a really dim OIII target (OU4) so I had to turn to my big reflector to get extra photons for additional contrast.
Part of the problem may be that a 3nm filter may not wok very well at f/2 but I still need to figure out how much I lose.
The palette is a modified SHO where I kept some green to showcase the weaker Ha regions. This may not be the most eye-pleasing color combination but possibly the most informative.
The Samyang 135mm lens was coupled to ZWO ASI1600 mono camera with a filter wheel. More acquisition details on my Astrobin page.