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Great Hercules Cluster, M13

Technical card

Resolution: 3026x2161

Dates: May 30, 2014

Frames: Baader Planetarium UV/IR Cut 2": 9x300" ISO800

Integration: 0.8 hours

Darks: ~50

Flats: ~30

Flat darks: ~30

Bias: ~50

Avg. Moon age: 1.18 days

Avg. Moon phase: 1.56%

Astrometry.net job: 361059

RA center: 250.417 degrees

DEC center: 36.464 degrees

Pixel scale: 1.232 arcsec/pixel

Orientation: 98.907 degrees

Field radius: 0.636 degrees

Locations: East Coast Star Party, Coinjock, North Carolina, United States

Description

M13 is a large globular cluster in the constellation Hercules. This is another image from the 2014 Spring East Coast Star Party.

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Processing Workflow (PixInsight)
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Pre-processing
1. Calibrate light frames using darks, bias, flats
2. Integrate using sigma clipping rejection.

Post-processing
1. Initial crop (Dynamic crop)
2. Reduce background gradient and neutralize background (DynamicBackgroundExtraction, subtract)
3. Neutralize background (BackgroundNeutralization)
4. Set white balance (ColorCalibration; use entire image since it is all stars)
5. Non-linear stretch (MaskedStretch script; target median background 0.15)
6. Set luminance coefficients to 0.333333 for RGB channels (RGBWorkingSpace).
7. Reduce background luminance noise (ACDNR to luminance with luminance mask)
8. Reduce background chrominance noise (ACDNR to chrominance with luminance mask)
9. Reduce green (SCNR)
10. Lower background brightness (CurvesTransformation)
11. Increase color saturation (CurvesTransformation w/ star mask selecting stars)
12. Cosmetic correction to a few spurious pixels in some stars that were over saturated (desaturation of the specific color with ColorSaturation using mask to select offending stars)
13. Lower background median brightness to 0.1 (CurvesTransformation)
14. Final Crop (DynamicCrop)
15. Set ICC profile to sRGB for web publishing (ICCProfileTransformation).

Comments

Author

Jason Tackett
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Great Hercules Cluster, M13, Jason Tackett

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