I attach NGC 2237 astrofoto, with exposures with narrow-band filters.
Corbera de Llobregat.Observatory Can Margarit.(Barcelona) Spain Date: 03 y 07-2013.
Telescope: Astrograph APM 107 f:4.9(Reduced with Riccardi reducer-flattener)
Mount: 10 MICRON GM 2000 camera SBIG STL 11000M
H alpha as R.
Or III as G.
S II as B
H-alpha: 6 x 1.200 sec bin 1-III: 3 x 1.200 seg bin 1.S-II: 4 x 1.200 seg bin 1
Calibrated with darks-flats-.:
CCDStack2 + Photoshop CS6 programs.