NGC 6866 is an open cluster in the constellation Cygnus, which appears slightly north of an imaginary line between the stars Sadr and Al Fawaris (Delta Cygni). At a distance of about 3900 light years, NGC 6866 contains about 100 stars [1,2] and is estimated to be 813 million years old. [2]
This region of the sky features extensive hydrogen-alpha emissions. The nebulosity in this image reminds me of looking up at the trunk of an enormous tree, in which case I suppose the cluster looks a bit like a beehive – but that name is already taken. The emission nebulae include several entries from Lynd’s Catalogue of Bright Nebulae (
LBN 238, LBN 242, LBN 252, LBN 260, and LBN 262) and Lynd’s Catalogue of Dark Nebulae (
LDN 887 and LDN 890). These faint hydrogen streamers are connected to the Propeller Nebula (Simeis 57) visually, if not physically.
In the lower right corner lies the planetary nebula
PK 78+ 5.1, which is also designated
Dd-1. Spanning about 22 arcseconds, [3] it is a bit too small of a target for a small refractor with an image scale of 1.4” per pixel. It’s worth noting that I used LRGB colors for the planetary nebula while the rest of the image has LHRGB colors. The "B" revision is a close crop of the PN in case you can't see it in the wide-field image.
Data collection for this image took quite a while due to ceaseless forest fire smoke invasions. My region has also had the most rainfall in July since record keeping began in 1826. I am glad to get one halfway decent image finished for summer of 2023, which is likely to end up ranking as the worst summer of my lifetime for astronomy (so far).
A few words about processing are in order. This image is an LHRGB composite, and my main processing platform is GIMP, as usual. The luminance channel is a sum of true luminance + starless H-alpha. The RGB channel is true RGB + starless H-alpha mapped to pure red. I tried to tone down the red hue a bit so it doesn't burn your eyes, but the nebulosity here is dominated by hydrogen emission, which is red. There's no reason to put an OIII filter onto this target as far as I know, except the PN could probably benefit from it. Noise reduction is a blend of the original image with Topaz AI noise reduction applied to the starless image (with AI sharpening turned off entirely). Star size reduction was carried out in ImagesPlus.
References
1. Astronomy magazine.
https://cs.astronomy.com/asy/m/starclusters/493397.aspx2. Bostancı, Z.F., Ak, T., Yontan, T., Bilir, S., Güver, T., Ak, S., Çakırlı, Ö., Özdarcan, O., Paunzen, E., De Cat, P. and Fu, J.N., 2015. A comprehensive study of the open cluster NGC 6866. Monthly Notices of the Royal Astronomical Society, 453(1), pp.1095-1107.
3. TheSkyX databases. Software Bisque.
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