A deep M51 through the integrated flux nebula. I've never noticed the dusty stuff in other RGB images but you can see some of it in Wise Band 3 infrared so it doesn't seem to be a processing artifact
The background is a bit ugly because I did stretch this fairly violently to show the IFN better...
Captured at SRO California, 14 Feb - 20 Apr, 2016
Scope: Ceravolo C300 @ f/4.9 = 1470mm FL
Mount: AP1100
Camera: FLI PL16803
Focuser: Atlas
Filters: Astrodon
Guiding: Lodestar II / Tak guide scope
Image scale: 1.26 arcsec/pixel
Exposures: 44x600s L, 46x1200s R, 16x1200s G, 18x1200s B, 38x1800s Ha (~53 hours)
Processing: PixInsight 1.8
Acquisition credit: John Kasianowicz, Daniele Malleo, Leonardo Orazi, Rob Pfile, Rick Stevenson and Jerry Yesavage.
Processing credit: Rick Stevenson
Full res version available on Astrobin:
http://www.astrobin.com/247447/None/
Cheers,
Rick.