The Crescent Nebula (NGC 6888)

Crescent Nebula
All Images Copyright Steve Cannistra

Please click here or on image for a medium size (35%).
Please click here or on image for a larger size (45%).
Please click here for a crop of NGC6888 (120%).

Magnitude:  10.0
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.

Photographic Details:
Date posted:  July 1, 2007.
Scope:  Takahashi FSQ106 at f5 on the G11 Losmandy Mount.
Autoguider:  SBIG ST-402 with e-finder.
Camera:  STL11K -20C.

Baader 7nm Ha filter.
Exposures:  6/23/07, 8 x 20'; 6/27/07, 8 x 20'.  Total exposure 5.3 hours.
Conditions:  Temperature 70-80 degrees F, good transparency, average seeing.
Post-processing:  Calibrated, aligned, and Sigma Clip combined in Maxim, followed by DDP in ImagesPlus (IP).  Further processing in Photoshop CS (16 bit format).

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