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Technical card

Imaging telescope or lens: Rokinon 16mm f2.0

Imaging camera: Canon 550D

Mount: Vixen Polarie

Software: Microsoft Image Composite Editor LightroomPixInsightPhotoshop

Resolution: 3600x2364

Dates: Aug. 11, 2016

Frames: 52x90" ISO1600

Integration: 1.3 hours

Darks: ~20

Flats: ~20

Bias: ~50

Avg. Moon age: 7.60 days

Avg. Moon phase: 52.34%

Astrometry.net job: 1262254

Description

“Dueling Galaxies”, Cape Hatteras National Seashore, North Carolina on the night of the Perseid meteor shower peak. 78 minute exposure at f/2.8.

Please see my blog for more information about this photo!
http://jasontackett-astrophotography.blogspot.com/2016/10/dueling-galaxies-at-cape-hatteras.html

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Processing Workflow
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PixInsight:
1. Initial crop (DynamicCrop).
2. Reduce gradient (DynamicBackgroundExtraction, subtract).
3. Neutralize background (BackgroundNeutralization).
4. Set white balance (ColorCalibration).
5. Reduce background noise (TGVDenoise with inverted luminance mask).
6. Mild non-linear stretch (HistogramTransformation, lower midtone slide by a modest amount).
7. Save as 16-bit tif.
8. Repeat the steps above with the five inividual images with meteors, adjusting thresholds as necessary. I also added chrominance noise reduction (MultiscaleMedianTransform to Chrominance) prior to the non-linear stretch. I ensured the median value of the individual meteor images matched that of the stacked master image.

Photoshop:
9. Add individual meteors to main image by using masks that select only each meteor and setting their layer blend mode to Lighten with the background layer being the stacked image.
10. Apply contrast curve to each layer containing a meteor to brighten the meteor and darken the residual background that was not masked out (Curves adjustment layer).
11. Save flattened image as 16-bit tif. Open in new PSD file for following steps - I probably could have used a Smart Object rather than creating a whole new PSD file, but this seemed cleaner.
12. Non-linear stretch using screen-mask-invert (SMI) technique (Lodriguss technique modified by Scott Rosen, described on the Astro Imaging Channel).
12a. Duplicate background layer, blur using Dust and Scratches filter, radius 6.
12b. Select original background layer and paste as layer mask on blurred layer, invert.
12c. Set blurred layer blend mode to Screen.
12d. Reduce background brightness to that of the original image with a Levels adjustment layer.
13. Save as 16-bit tif.

PixInsight:
14. Set luminance coefficients to 0.333333 for RGB channels (RGBWorkingSpace).
15. Reduce green cast (SCNR to green, 0.60 w/inverted luminance mask).
16. Increase color saturation (CurvesTransformation to S w/luminance mask).
17. Increase galaxy brightness (ExponentialTransformation, Power of Inverted Pixels order 0.8 w/luminance mask)
18. Sharpen (MultiscaleMedianTransform to lightness, +0.01, +0.02 to layers 3 and 4)
19. Increase color saturation (ColorSaturation to all colors except bluish-purple which was a color cast left over from so-so DBE, w/luminance mask)
20. Set blackpoint (HistogramTransformation, raise black point slider)
21. Resample to 3600px wide (Resample)

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Author

Jason Tackett
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Dueling Galaxies , Jason Tackett