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M17 "The Swan Nebula" in Sagittarius




Scope: C8 at f/6.3; Location: Laguna Mountains, CA;  18 July, 2009; Camera: Canon XT 350D (Baader ACF modified)

Exposure: 17 x 6 min  (unfiltered) and 10 x 8 min (H-Alpha EOS Clip)  ISO 800 , 6/5 Darks, no Flats 

Processing: Images were captured with DSLR Focus  and saved as RAW file format. Unfiltered and H-Alpha exposures were decoded and dark corrected in IRIS. Exposures were aligned and stacked in IRIS with Sigma Median.  Dark point equalization and rough color balance  were done on the Unfiltered exposures in IRIS. On the H-Alpha exposure stack, RGB channels were separated and Red and Green were added (there is some signal crossed to Green in the DeBayering).. Gamma adjustments were also done in Iris.  The unfiltered  exposure stack was blended with the H-Alpha stack as a luminance layer to bring out H-Alpha details.   A second Luminance layer consisting of the image in grayscale was combined with the color channels which were softened and saturated before being recombined with the grayscale Luminance. Final stretching and touch up was done in PhotoShop.     Final Image size is approximately 3450x2300 - re-sampled to 2400x1600.

North is up in this image.  This image is guided.  M17 is sometimes known as the Swan Nebula, sometimes as the Omega Nebula, and sometimes as the Horseshoe Nebula. This region is  a star forming region  with young stars exciting surrounding Hydrogen to light emission. Lighter central bar is  believed to emit reflected light from the brighter stars as well. Distance estimates vary but the approximate distance from Earth is about 5,000 light years.   The Horizontal FOV is about 55 min.

Image Center is approximately - Equatorial 2000: RA: 18h 20m 35s Dec: -1610'49"

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