2019 July 25 ~ LDN 617 (dark nebula in Aquila)

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Photographed at Algonquin Provincial Park, Ontario, Canada

(285 km by road north of Toronto)

between 00.00 and 00.17 EDT

* Altitude of the nebula at time of exposures: 46°

* Temperature 17° C.

 

* Total exposure time: 8 minutes

* 660 mm focal length telescope

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Description:

 

The northern Milky Way in the constellations Scutum and Aquila is dotted with dark gas clouds or nebulae that hide the lights from tens of thousands of more distant stars in our galaxy.

 

These dark nebulae were catalogued by American astronomer Beverly Turner Lynds, who painstakingly inspected hundreds of red and blue plates from the Palomar Sky Survey and published her catalog of dark nebulae in 1960. These objects are now all given the prefix "LDN" (for "Lynds Dark Nebulae").

 

LDN 617 is large, about 50' x 10' in size, with its long axis oriented almost due east-west in the sky. It is a very difficult object to spot visually, however; the camera does a much better job recording this nebula.

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Technical information:

 

Nikon D810a camera body on Tele Vue 127is (127 mm - 5" - diameter) apochromatic astrograph, mounted on Astrophysics 1100GTO equatorial mount

 

Eight stacked subframes; each frame:

ISO 4000; 1 minute exposure at f/5.2, unguided

(with LENR - long exposure noise reduction)

 

Subframes stacked in RegiStar;

Processed in Photoshop CS6 (brightness, contrast, levels, colour balance)

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Done