Planetary Nebulae (5 objects)
Famous planetary nebula, the Helix in Aquarius. A pretty deep exposure (51 hrs) processed to bring out very faint outer features. H-alpha 31 hrs, OIII 20hrs. Mostly unbinned, some 2x2 binned, Mosaic of not-qute overlapping images from Aspen 16M and STL11000M. PlaneWave 20" CDK. Of great interest are the cometary knots seen as clumpy yellow-green streaks against the blue, radiating outward away from the blue-white central white dwarf. Notice the extremely faint chevron-like bow-wave shock fronts toward 9 o'clock., 10:30, and 11 o'clock. These structures average a flux of around just one photon per pixel per hour above background. There is a background galaxy clearly visible through the shocked material at 10:30, and several other tiny galaxies are visible in the image. North up. FOV approx half a degree.
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