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Contains:  NGC 884, Double cluster, NGC 869, The star 7Per
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Double Cluster, h and Chi Persei, 


            Jason Tackett
Double Cluster, h and Chi Persei

Double Cluster, h and Chi Persei

Technical card

Resolution: 3557x2461

Dates:Oct. 5, 2014

Frames: 43x120" ISO400

Integration: 1.4 hours

Darks: ~30

Flats: ~11

Bias: ~50

Avg. Moon age: 11.42 days

Avg. Moon phase: 87.88% job: 384491

RA center: 35.170 degrees

DEC center: 57.144 degrees

Pixel scale: 1.240 arcsec/pixel

Orientation: 5.289 degrees

Field radius: 0.745 degrees

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


Double Cluster is the popular name for the rich open star cluster pair in the constellation Perseus, h and Chi Persei (NGC 869, NGC 884). At a distance of 7500 light years away, this 12.8 million year old cluster is the jeweled handle of Perseus’ sword.

Processing Workflow (PixInsight)

1. Calibrate light frames using darks, bias, flats
2. Integrate using Windsorized sigma clipping rejection.

1. Initial crop (Dynamic crop)
2. Reduce background gradient and neutralize background (AutomaticBackgroundExtractor, division)
3. Reduce background gradient and neutralize background (DynamicBackgroundExtraction, division)
4. Neutralize background (BackgroundNeutralization)
5. Set white balance (ColorCalibration; use entire image since it is all stars)
6. Set luminance coefficients to 0.333333 for RGB channels (RGBWorkingSpace).
7. Noise reduction (MultiscaleLinearTransform w/ inverted luminance mask)
8. Non-linear stretch (MaskedStretch script; target median background 0.15)
9. Increase contrast (CurvesTransformation)
10. Reduce green (SCNR w/ range mask protecting stars)
11. Reduce background chrominance noise (ACDNR to chrominance with luminance mask)
12. Increase color saturation (CurvesTransformation w/ star mask selecting stars)
13. Balance background colors (CurvesTransformation)
14. Clean up dark pixels (Pixel Math [Shwartz script])
15. Lower background median brightness to 0.1 (CurvesTransformation)
16. Final Crop (DynamicCrop)
17. Set ICC profile to sRGB for web publishing (ICCProfileTransformation).

Manfred Schwarz’ galaxy tutorial:



Jason Tackett
License: Attribution Creative Commons

Sky plot

Sky plot


Double Cluster, h and Chi Persei, 


            Jason Tackett

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