Second lowest of all Messier objects in surface brightness, M74 is a bit of a challenge to process. It required a lot of stretching and contrast enhancements and that always stresses out my stars. Interestingly, the lowest surface brightness M object is M101!
M74 is 10' in diameter so it makes up for being dim by being big. I've known some people like that
At 32 million ly away, Ha signal is present and worth capturing. I always like to add Ha subtley and did so here by first cleaning the Ha master of continuum and then adding to to the linear red at half strength after color calibration. I calibrate first to prevent the Ha regions from causing the other red areas to be under-represented. This just highlights the Ha emission areas. I also added 5% of the Ha to the blue to keep the added data a more accurate magenta color rather than straight red. This emulates the Hbeta that would be present too.
So why is this so dim? I haven't seen any explanation. It does not appear to be obscuring dust from our galaxy as the surrounding background was one of the flatest I've seen in a while.
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