The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light years away. It was discovered by Friedrich Wilhelm Herschel in 1792. 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 250,000 to 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.

It is a rather faint object located about 2 degrees SW of Sadr. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8cm (with filter) can see its nebulosity. Larger telescopes (20cm or more) reveal the crescent or aEuro sign shape which makes some to call it the “Euro sign nebula”.

Imaging telescopes or lenses: CELESTRON Edge HD 8
Imaging cameras: QSI 583 wsg
Mounts: Astro-Physics Mach 1 GTO
Guiding telescopes or lenses: CELESTRON Edge HD 8
Guiding cameras: SX Lodestar
Software: Maxim DL 5 MaximDL 5, Pleiades Astrophoto Pixinsight 1.8, Adobe Photoshop 6 CS
Filters: Astrodon Ha 5mm, Astrodon OIII 3nm
Accessories: SXV-AO-LF
Frames: 36×1800″

Autor: Daniele Malleo

AstroPhotography of the day by SPONLI

22 January 2014

We select the best works of amateur astrophotographers with details of equipment, shooting processing etc.