2016 Sept. 25 ~ NGC 6888, the Crescent Nebula in Cygnus

******************************************************************************

Photographed at Algonquin Provincial Park, Ontario, Canada, between 00.12 and 00.45 EDT

(285 km by road north of Toronto)

* Altitude of the nebula at time of exposures: 55°, decreasing to 50°

* Temperature 5° C.

 

* Total exposure time: 15 minutes

* 2483 mm focal length telescope

___________________________________________

Situated in the heart of our Milky Way galaxy as it passes directly overhead during the summer in the northern hemisphere, the Crescent Nebula is a half ring of ionized hydrogen gas, which glows with a characteristic red-pink colour. The nebula has an angular size of 20' x 10', which makes it about 1/3 the apparent size (in area) of the Moon as seen from Earth.

 

From Wikipedia:

The Crescent Nebula is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. 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 [the bright star] Sadr. For most telescopes it requires a UHC or OIII filter to see. Under favorable circumstances a telescope as small as 8 cm (with filter) can see its nebulosity. Larger telescopes (20 cm or more) reveal the crescent or a Euro sign shape which makes some to call it the "Euro sign nebula".

 

Click here to see a wider angle view of this region, which shows adjacent larger diffuse hydrogen gas clouds in the constellation Cygnus:

www.flickr.com/photos/97587627@N06/29549773051

 

Click here to see the equipment used to photograph this galaxy:

www.flickr.com/photos/97587627@N06/29939255555

___________________________________________

 

Nikon D810a camera body at prime focus of Meade 30 cm (12") LX-850 Schmidt-Cassegrain telescope, mounted on Astrophysics 1100GTO equatorial mount

 

Fifteen stacked frames; each frame:

2483 mm focal length; ISO 10,000; 60 seconds exposure at f/8, unguided

(with LENR - long exposure noise reduction)

 

Subframes stacked in RegiStar;

Processed in Photoshop CS6 (brightness, contrast, levels, sharpening)

******************************************************************************

Done