Unavoidable Noise

M101, the “Pinwheel Galaxy”.  It has low surface brightness, and the sky at Songbird Observatory, San Francisco East Bay Hills, is almost always at least a little hazy, with an ever-present skyglow from the nearby cities. The results are always  noisy –like an analog photos with lots of grain:

M101 -- full noise

Further processing with PixInsight and Gimp lessens the obvious noise, but you also lose some of the delicate shading in the galaxy:

M101 with more processing 

I can’t see this object (it seems so strange to use the word “object” to refer to an entire galaxy…) with my naked eye.

In fact, most nights I can’t make out more than a couple of constellations — if I didn’t use software to point the telescope, I would not be able to find M101.

How, then, do I even know this is M101 I photographed? I can compare it with the Hubble view.

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