NGC 6357 in Scorpius
CLICK ON IMAGE FOR FULL SIZE VIEW (2400x1857)
Scope: Mak-Newt 152 mm f/4.8, Location: Laguna Mountains, CA, 4 July 2010 Camera: ST8300M
Exposure: 10 x 7 min H-Alpha Exposure (1x1), 8 x 4 min UV/IR Block Luminance, 8 x 2.5 min RGB exposures (2x2).
Processing: Images were captured with CCDSoft. Aligned/stacked and dark subtracted in Astroart ; Sigma Combine method was used for stacking subs. All channels were scaled and rough color balanced in Astroart. Central Gradient removal was done in Astroart. Channels were co-registered in Astroart. The 7 minute H-Alpha exposures were combined with the 4 minute luminance exposures for the main luminance construction with level adjustments and curves to bring out object features. LRGB combine was done in Photoshop. Saturation adjustments were selectively applied excluding the brighter areas. Bright area exclusion on some portions of Levels, Curves, and Saturation was to avoid core over brightening and out of Gamut. A light background noise reduction was applied in PixInsight LE (SGBNR). Sharpening was done on the luminance channel. Final touches and color balance in Photoshop. Final Image size is approximately 3352x2532 (resized to 2400x1857).
North is up in this image. NGC 6357 is located in the constellation of Scorpius. This object appears mostly red because it is a Hydrogen Alpha emission nebula and its light travels through a fair amount of interstellar dust to reach Earth. The dust tends to reduce transmission of shorter blue wavelengths and less so the longer red wavelengths.. This image replaces an earlier image of this region and can be seen in the Archives here. Horizontal FOV is 83 arc minutes.
Image center is located approximately - Equatorial 2000: RA: 17h 25m 01s Dec: -34°13'00"
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