The Crescent Nebula (NGC 6888)
Size: about 20'
Distance: 4,700 light years
Position Angle (Pinpoint): +11 degrees
RA (J2000): 20h 12m 11s
Dec (J2000): +38 degrees 20' 28"
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,
This represents the first light image for the VC200L in f6.1
configuration (based upon plate solve results), yielding a focal length
of 1228mm and an image scale of 1.14 "/pixel. Details may be
found in the Equipment
Date: July 2, 2008
Scope: Vixen VC200L at f6.1 (FL = 1228 mm) on the
Autoguider: SBIG ST-402 with
60mm guidescope, focal length 227mm.
Camera: Apogee U32 -20C.
Exposures: Ha: 16 x 15' = 240'
(unbinned); Total exposure 4
Conditions: A clear night sandwiched in between a
terrible stretch of weather here in New England. Seeing
only in the range of 3.5".
Calibrated, debloomed, aligned, and Sigma
in Maxim. DDP
in ImagesPlus (IP). Deconvolution (25 iterations) in AIP4WIN.
Further processing in Photoshop
Given the high density of stars in this region, I used one pass of a
minimum filter (radius 1) with 50% opacity, masked only to affect the
stars, in order to reduce their size and draw attention towards the
center of the field.
note: Graphics on this website
may not be reproduced without author permission.
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