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)