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Owl Cluster, NGC 457

Technical card

Resolution: 3294x2369

Dates: Oct. 8, 2014Oct. 16, 2014

Frames:
1x120" ISO400
62x30" ISO400
3x300" ISO400
47x60" ISO400

Integration: 1.6 hours

Darks: ~30

Flats: ~30

Bias: ~50

Avg. Moon age: 18.29 days

Avg. Moon phase: 73.94%

Astrometry.net job: 407544

RA center: 20.128 degrees

DEC center: 58.169 degrees

Pixel scale: 0.930 arcsec/pixel

Orientation: 8.145 degrees

Field radius: 0.524 degrees

Locations: Backyard, Hampton, VA, Hampton, VA, United States

Description

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

Post-processing
1. Initial crop (Dynamic crop) .
2. Remove vertical banding which seems to appear in my ISO400 subs that are 30 seconds or less. Perhaps my darks aren’t quite the right temperature (CanonBandingRedctionScript).
3. Reduce background gradient (AutomaticBackgroundExtraction, subtraction).
4. Reduce background gradient and neutralize background (DynamicBackgroundExtraction, subtraction).
5. Neutralize background (BackgroundNeutralization).
6. Set white balance (ColorCalibration; use entire image since it is all stars).
7. Set luminance coefficients to 0.333333 for RGB channels (RGBWorkingSpace).
8. Reduce background noise (MultiscaleLinearTransform w/ luminance mask).
9. Non-linear stretch (MaskedStretch script; target median background 0.15).
10. Increase contrast (CurvesTransformation “s” curve).
11. Reduce green (SCNR w/mask targeting background).
12. Reduce chrominance noise (ACDNR to chrominance with luminance mask).
13. Increase color saturation (CurvesTransformation).
14. Reduce saturation artifact in brightest stars (InterchannelCurves, reference:saturation, target: c; w/mask selecting brightest stars).
15. Brighten stars slightly (CurvesTransformation).
16. Reduce slight red cast by lowering blackpoint of red channel, lower median background brightness to 0.1 (HistogramTransformation).
17. Reduce large scale chrominance noise in background (InterChannelCurves, reference: L, target: c, w/mask protecting stars)
18 Final Crop (DynamicCrop).
19. Set ICC profile to sRGB for web publishing (ICCProfileTransformation).

Comments

Author

Jason Tackett
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Owl Cluster, NGC 457, Jason Tackett

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