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NGC 6888 is, in many ways, an unusual nebula. It is the result of the evolution of its central star HD 192163 (also known as WR 136, because it is a Wolf Rayet star). It started (about 5 Million years ago) as a supergiant O star, with a mass higher than 30 solar masses. Short ago (cosmologically speaking…) it became a red supergiant. It was shedding layers at a tremendous speed. It then reached its current phase: Wolf Rayet star. This star will end its days exploding as a supernova, about 100,000 years in the future. The strong stellar winds have shaped this nebula, and the radiation shock waves have excited it to emit in the two most common emission lines: Halpha and OIII. For this image, also 6 hours taken through a NII filter were added. Actually, there was not much difference between the 3nm Halpha and the NII images. The filters were then mapped to reproduce, as much as possible, the natural color of this nebula (Ha and NII: Red; OIII: Green and Blue).
This image has a special meaning to me, because it is the first image that I have been able to take with the new 24″ telescope. This telescope is located at the premises of New Mexico Skies close to Mayhill, NM, USA.
Name(s): NGC 6888. Caldwell 27. Crescent Nebula.
Type: Emission Nebula
RA: 20h 12m 29.6s
Dec: +38º 25’ 02”
Size (arcmin): 25×14
Distance: 5,400 ly
Date: 2019-09-19 to 2019-09-30
Location: New Mexico Skies, Mayhill, NM, USA
Size (arcmin): 32×32
Telescope: 24″ f/6.5 Reflector
Camera: FLI PL16803 (4096x4096pix)
Guiding: Astrodon MonsterMOAG off-axis guider
Total exposure: 24.8 hours (Ha: 12h=18x40min; OIII: 5h20min=8x40min; NII: 6h=9x40min; RGB: 1h 30m)
Processing: CCDStack, Photoshop CC 2020