Paul C. Swift
Imaging telescopes or lenses: Vixen VSD100 f/3.8 Astrograph
Imaging cameras: Starlight Express SXVR-H18
Mounts: Sky-Watcher NEQ6 Pro
Guiding telescopes or lenses: Vixen VSD
Guiding cameras: sx loadstar
Software: PixInsight 1.8, Photoshop CS5
Filters: Baader O III 8.5nm, Baader Ha 8.5nm
Accessories: Starlight Xpress USB filter wheel, Starlight Xpress Lodestar Guider
Dates: July 9, 2015, July 12, 2015, July 23, 2015
Baader Ha 8.5nm: 13×1800″ bin 1×1
Baader O III 8.5nm: 18×1800″ bin 1×1
Baader SII 8.5nm: 14×1800″ bin 1×1
and second panel:
Baader Ha 8.5nm: 8×1800″ bin 1×1
Baader O III 8.5nm: 8×1800″ bin 1×1
Baader SII 8.5nm:8×1800″ bin 1×1
Avg. Moon age: 24.76 days
Avg. Moon phase: 25.31%
Locations: Home observatory, Valencia, Spain
This is a combination – mosaic of wide field Narroband data, with added close-up data of the Crescent nebula area acquired with my RC8 . This is the third part of my Gamma Cyg nebula project.
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 a Euro sign shape which makes some to call it the “Euro sign nebula”.