SUPERCEDED-NEWER VERSION AVAILABLE---M17 - The Omega Nebula in Sagittarius
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M17 is one of the treasures of Sagittarius. Commonly called the Omega Nebula, it also known as the Swan Nebula (because it looks like a swan) as well as the Checkmark Nebula, the Lobster Nebula, and NGC 6618
In this image, North is Down. This image is cropped to 81% of the original full frame.
Exposure Details |
Lens |
Celestron C-8 SCT with Celestron focal reducer |
Focal Length |
1260mm |
Focal Ratio |
f/6.3 |
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Mount |
Schaefer GEM - 7 1/2 |
Guiding |
80mm f/11 guidescope with PHD Guiding |
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Camera |
Canon 20Da |
Exposure |
87 subexposures of 180 seconds each at ISO 1600 - about 4 1/3 hours total |
Calibration |
30 darks, 30 flats, 30 bias |
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Date |
August 28, 29, and 30, 2011 |
Temperature |
70F on 8/28, 65F on 8/29, 61F on 8/30 |
SQM Reading |
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Seeing |
4 of 5 on all 3 nights |
Location |
Pine Mountain Club, California |
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Software Used |
Images Plus 4.0 for camera control, calibration, stacking, digital development, and initial smoothing. Photoshop CS5 used for flat fielding, curves, color correction, saturation adjustments, star shrinking, and high pass filter. Carboni Actions for additional saturation adjustments and noise reduction. |
Notes |
After reprocessing this image several times, I was finally able to bring out the faint outer nebulosity. |
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