NGC 6888 - The Crescent Nebula in Hubble palette

Posted by CraigAndTammy
on Wednesday, June 26, 2013

Discovered in 1792 by Friedrich Wilhelm Herschel, the Crescent Nebula (NGC6888, Caldwell 27, LBN 203, Sharpless 105), 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.

This image is in the standard Hubble Space Telescope (HST) palette where SII = Red, H-alpha = Green, OIII = Blue.

Telescope: Sky Watcher Quantum 120 Apo @ f/7
Accessories: SW Quantum matched flattener; Dew control by Dew Buster; Alnitak Flat-Man; Gerd Neumann Aurora flat panel
Mount: Takahashi EM-200 Temma2
Camera: QSI583wsg CCD @ -10.0C
Guiding: Starlight Xpress Lodestar via PHD
Filters: Astrodon 5nm Ha, OIII, SII
Exposure: 12 x 20min. binned 1x1 each in Ha, OIII, SII
Acquisition: ImagesPlus 5.0 Camera Control
Processing: PixInsight 1.8; Adobe PhotoShop CS5; Noel Carboni’s Actions
Date(s): June 3, 12, 13, 14, 2013
SQM reading (begin - end): N1:19.11 – 19.28; N2:18.92 – 19.15; N3:18.92 – 19.54; N4:18.89 – 19.39
Temperature (begin - end): N1:65.4ºF – 61.6ºF; N2:83.7ºF – 80.6ºF; N3:73.8ºF – 67.1ºF; N4:70.7ºF – 64.9ºF
Capture conditions: N1 - transparency: Avg 3/5; seeing: Avg 3/5; N2 - transparency: Above Avg 4/5; seeing: Poor 2/5; N3 - transparency: Above avg 4/5; seeing: Poor 2/5; N4 - transparency: Avg 3/5; seeing: Avg 3/5
Location: Hendersonville, TN, USA

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