After extremely helpful input from many of you, I could see that my previous attempt at processing was overly sharpened, leading to nasty artifacts.
I've tossed out two of the original seven luminance frames as being the least sharp. I've done less deconvolution and no wavelet sharpening or noise reduction. I've tried harder controlling the saturation of the background galaxies, stars, and the main galaxy. Also, the measured mean colour for the galaxy is now very close to neutral. I've also been careful not to burn out the central region.
The result is less "punchy" from across the room, but I think better at the single pixel level. Thanks to everyone for the guidance on that score. The original image (2.3MB) is here.
I think we tend to display this galaxy south up, because that puts the more contrasty edge apparently closer to the viewer, creating a pleasing visual illusion. So south up it is.
L: 5x 1hr unbinned, RGB 1hr each 2x2 binned. Aspen 16M on 20" PlaneWave.
I like that. Very nicely done. A couple of minor red dots (artifacts in the background . The Photoshop healing tool gets rid of those. Not sure how they creep into an image but I occassionally seem them also. Often in other colours as well.
Those dust streamers are most intriguing. David Malin et al (http://arxiv.org/abs/astro-ph/9407074) talked about a "boiling galactic disc" in which star formation, supernova explosions, and magnetic fields might have produced these vertical streamers. Later work at ESO seems to favour star formation only, but it's a bit technical for me to understand, and they're more talking about carbon monoxide than dust.
So which bits are the streamers, exactly? I've indicated on the attached image some very long, relatively narrow, orange-brown streaks rising approximately but not exactly perpendicular to the plane of the galaxy. I'm guessing that these are they. It helps to screw your eyes up (but not shut tight!!) to see them best. Then they are very obvious. There are probably twice as many as I've shown, but these are the best ones. The ones closest to the galactic core (upper left) are about twice as long and three times thicker than the ones further toward the suburbs (bottom right). They are definitely not part of the spiral structure, because they are more or less at right angles to the spiral.
