The Crescent Nebula in Hydrogen Alpha (NGC 6888)
Size: about 20'
Distance: 4,700 light years
RA: 20h 12m 48s
Dec: 38 degrees 19' 00"
The Crescent Nebula is not a typical supernova remnant
like the Veil. It is probably a result of the slow
release of large amounts of gas from the dying central star seen in the
above photograph, known as Wolf-Rayet 136, which has not yet gone
supernova. The stellar winds
resulting from the release of this star's outer envelope compress and
excite surrounding hydrogen gas, resulting in Ha emission and the
characteristic layered texture to NGC 6888. More information
about this interesting region of space can be found here.
Date: July 3, 2004
Sky 90 at f4.5 with field flattener/focal reducer, on the G11 Losmandy
Autoguider: SBIG STV with
Ha filter (13 nm bandpass).
Exposures: 17 x 5' each, binned
1 x 1, 85
Conditions: Temperature 60 degrees F; below average
transparency; very humid; excellent seeing; calm.
Post-processing: No dark, bias, or flat frames used. Two-star aligned
MaximDL; Sigma combined using RC Sigma Reject MaximDL, followed by DDP
in ImagesPlus (IP). Subsequent
levels and curves adjustments in Photoshop CS (16 bit format). I
purposefully avoided overprocessing this area, since I like a more
natural look to this region.
note: Graphics on this website
may not be reproduced without author permission.
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