2018 May 13/14 ~ Gum 17 & 15 Nebulae in the constellation Vela [WITH LABELS]

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Photographed outside Uluṟu-Kata Tjuṯa National Park, Northern Territory, Australia (440 km by road southwest of Alice Springs), long. 131.04° E., lat. 25.22° S., between 23.27 and 00.00 CAST (Central Australian Standard Time)

 

* Altitude of centre of frame at time of exposures: 25°, declining to 19°

* Temperature 15° C.

* Total exposure time: 15 minutes

* 540 mm focal length telescope

* field of view: 3° wide by 2° high

* co-ordinates of centre of frame: R.A. 8 h 53 m, Dec. -42° 12'

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Description:

 

The Gum catalog is an astronomical catalog of 84 emission nebulae in the southern sky. It was made by the Australian astronomer Colin Stanley Gum (1924-1960) at Mount Stromlo Observatory using wide field photography.

 

Gum 15 (upper right) is an ionized hydrogen gas cloud located about 3,000 light years from our solar system.

 

The much larger Gum 17 (centre left), which domintaes the frame, has an uncertain distance. If the source of the excitation of the hydrogen gas (which makes it glow) is the Trumpler 10 star cluster (just to the right of and a little below centre), then the distance of the nebula is about 1,300 light years. If the source is SAO 220552 (the bright hot blue star dead centre in the nebula), then the nebula is much further away, at about 3,200 light years.

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This is the telescope and mount that I used for my astrophotography on this trip:

www.flickr.com/photos/97587627@N06/28602350028

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For a version of this photo WITHOUT LABELS, click on your screen to the LEFT of the photo, or click here:

www.flickr.com/photos/97587627@N06/43843928962

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Technical information:

 

Nikon D810a camera body on Tele Vue 101is 101 mm (4") apochromatic refracting telescope, mounted on Sky-Watcher HEQ5 equatorial mount

 

Fifteen stacked subframes - each frame:

ISO 6400; 1 minute exposure at f/5.4, 540 mm focal length, unguided (with LENR - long exposure noise reduction)

 

Subframes stacked in RegiStar;

Processed in Photoshop CS6 (curves, levels, brightness, contrast, colour balance, star bloating reduction)

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Done