Not imaged this before until now, and wow, honestly the Ha and OIII emissions are unbelievable and so very different. When I combined this bi-colour image I had to go back and check the master OIII and Ha frames to verify. Sure enough, in the top right there was dense Ha nebulosity, and no OIII apparent, and exactly the opposite in the lower left. Consequently, you have this incredible result. This was a real joy to put together.
http://www.martinpughastrophotograph...SNRPortion.jpg (3mb)
15 hours all up, bi-colour Ha and OIII.
Thanks for looking.
Martin