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Technical card

Resolution: 5170x3455

Dates: Oct. 25, 2014

Frames:
17x10" ISO400
10x150" ISO400
20x30" ISO400
12x300" ISO400
8x450" ISO400
10x60" ISO400

Integration: 2.8 hours

Darks: ~30

Flats: ~30

Bias: ~50

Avg. Moon age: 1.06 days

Avg. Moon phase: 1.26%

Astrometry.net job: 1137353

RA center: 83.663 degrees

DEC center: -5.665 degrees

Pixel scale: 0.932 arcsec/pixel

Orientation: 95.764 degrees

Field radius: 0.804 degrees

Locations: Staunton River State Park, Red Oak, VA, United States

Description

Captured this image of the Orion Nebula at the Staunton River Star Party. It is composed of exposures of six different lengths to capture the expansive dynamic range of this compelling object.

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Processing Workflow (PixInsight)
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Pre-processing
1. Calibrate light frames using darks, bias, flats
2. Integrate each set of given exposure length separately using Windsorized sigma clipping rejection.

Post-processing
1. Combine multiple exposures into 64 bit image (HDRComposition)
2. Compress dynamic range (HDRMultiscaleTransform).
3. Initial crop (Dynamic crop) .
4. Reduce background gradient and neutralize background (DynamicBackgroundExtraction, subtraction).
5. Neutralize background (BackgroundNeutralization).
6. Set white balance (ColorCalibration).
7. Set luminance coefficients to 0.333333 for RGB channels (RGBWorkingSpace).
8. Non-linear stretch (MaskedStretch script; target median background 0.15).
9. Increase contrast (CurvesTransformation w/mask protecting stars).
10. Increase local contrast (LocalHistogramEqualization w/mask selecting nebula).
11. Stretch to bring out faint dust (ExponentialTransformation w/mask protecting stars).
12. Increase contrast slightly (CurvesTransformation).
13. Reduce luminance noise (ACDNR to luminance with luminance mask),
14. Reduce chrominance noise (ACDNR to chrominance with luminance mask),
15. Reduce green (SCNR),
16. Mend saturation artifact in brightest stars (InterchannelCurves, reference:saturation, target: c; w/mask selecting brightest stars).
17. Increase contrast slightly (CurvesTransformation),
18. Increase color saturation (CurvesTransformation w/ mask selecting nebula only),
19. Increase orange color saturation to bring out color in dust (ColorSaturation w/ mask selecting nebula only),
20. Increase color saturation of stars (ColorSaturation w/ mask selecting stars),
21. Sharpen (MultiscaleMedianTransform w/mask strongly protecting stars).
22. Another gentle hit of luminance noise reduction (ACDNR to luminance with luminance mask).
23. Reduce star sizes (MorphologicalTransformation w/mask selecting stars).
24. Lower background median brightness to 0.1 (CurvesTransformation).
25. Final Crop (DynamicCrop).
26. Set ICC profile to sRGB for web publishing (ICCProfileTransformation).

Comments

Author

Jason Tackett
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Orion Nebula, Jason Tackett

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