The Crescent Nebula (NGC 6888) in HaRGB

Posted by CraigAndTammy
on Thursday, July 15, 2010

by Craig and Tammy Temple

 

The Crescent Nebula (NGC6888, Caldwell 27, LBN 203), also known as "Van Gogh's Ear" is a magnitude 7.40 emission nebula in the constellation Cygnus (The Swan). It is formed by the violently fast stellar winds emanating from a Wolf-Rayet star (WR 136, HD192163) colliding with the slower gases that were shed by the same star many thousands of years ago when it was a red giant. The gaseous shell is approximately 25 light-years across and 5,000 light-years distant. It is predicted that the central Wolf-Rayet star will eventually explode into a supernova in approximately 100,000 years.

RGB Color Data:
Telescope: Astro Tech AT8IN 8” f/4 Newtonian
Accessories: Baader MPCC
Mount: Orion Atlas EQ-G controlled by EQMOD
Guiding: TS-OAG9 Off-axis, using Orion StarShoot AutoGuider
Camera: Canon Digital Rebel T1i, Hap Griffin Baader modified
Filters: Astronomik CLS-CCD EOS Clip
Exposure: best 57/66 x 180s @ ISO 800 (2hr. 51min.)
Acquisition: ImagesPlus 4.00 beta 1 Camera Control
Processing: ImagesPlus 3.80a – Calibrated, registered, min/max averaged, DDP
Post-processing: Adobe Photoshop CS4; Gradient XTerminator; Noise Ninja
Date(s): June 13, 2010
Temperature(s): 82ºF (dropped to 78ºF)
SQM reading (begin - end): 19.34 - 19.32

Hydrogen-alpha Data:
Telescope: Astro Tech AT8IN 8” f/4 Newtonian
Accessories: Baader MPCC
Mount: Orion Atlas EQ-G controlled by EQMOD
Guiding: TS-OAG9 Off-axis, using Orion StarShoot AutoGuider
Camera: Canon Digital Rebel T1i, Hap Griffin Baader modified
Filters: Astronomik 6nm H-Alpha EOS Clip
Exposure: 25 x 900s @ ISO 1600 (6hr. 15min.)
Acquisition: ImagesPlus 4.00 beta 1A(N1) beta 2(N2) Camera Control
Processing: ImagesPlus 3.80a – Calibrated, registered, min/max averaged, DDP
Post-processing: Adobe Photoshop CS4; Noise Ninja
Date(s): July 3 & 7, 2010
Temperature(s): N1:79ºF (dropped to 74ºF); N2:82ºF (dropped to 78ºF)

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