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Harel Boren | all galleries >> International Acknowledgements - APODs and Publications > The Crescent Nebula - NGC 6888, C27, Sharpless 105 - 1900pix version
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The Crescent Nebula - NGC 6888, C27, Sharpless 105 - 1900pix version
April 27, 2009 Harel Boren

The Crescent Nebula - NGC 6888, C27, Sharpless 105 - 1900pix version

Km. 101, East Negev Desert, Israel

Canon XSi, modded, Total Ha(HaR)GB 128 min. = RGB 19x4 min., Ha 13x4 min., ISO 1600
LXD75-SN10 OTA, Baader MPCC, Baader 7nm Ha Filter, EQ6 mount, guided w/PHD and EQMOD

For me this image represents many "firsts" and personal records... The first image composed of Ha and RGB exposures; The first image where I use 4 minute exposures; and the image with the longest total exposure. Many photons contributed to this image: 128 minutes of 10" at F4 are "equal" to a 4 x 2.5 x 128 = 1280 min (~21 hours) of exposure, in a "standard" system of 5" at F/6.3. They've also succeeded in the task of traveling 5000 years all the way to the XSi chip.

And about the object:

The Crescent Nebula (NGC 6888 or Caldwell 27) is an emission nebula in the Cygnus constellation, about 5000 light years away. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray emitting temperatures. [Text taken as is from http://en.wikipedia.org/wiki/Crescent_Nebula].

The area imaged is saturated with interstellar material, and the glowing red hydrogen clouds showing in the image show that very well.


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