A giant nebula in M33 ... NGC604 is over 40 times the size of the visible portion of the Orion Nebula. It is over 6300 times more luminous than the Orion Nebula, and if it were at the same distance it would outshine Venus.
Difficult to merge the Ha signal, the appareance of galaxy change drammatically, I tried a 100% crop:
http://www.starkeeper.it/NGC604.htm
Thanks for looking
All the best,
Leo