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Flaming Star Nebula in Auriga

Technical card

Resolution: 4393x3138

Dates: Oct. 16, 2015Oct. 17, 2015

Frames: 41x300" ISO1600

Integration: 3.4 hours

Darks: ~30

Flats: ~30

Bias: ~40

Avg. Moon age: 3.18 days

Avg. Moon phase: 11.19%

Astrometry.net job: 904216

RA center: 79.212 degrees

DEC center: 34.508 degrees

Pixel scale: 0.930 arcsec/pixel

Orientation: 92.823 degrees

Field radius: 0.697 degrees

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

Description

Here is a capture of the Flaming Star Nebula in Auriga that I captured at the Staunton River Star Party in October 2015. It’s been a busy several months - I can’t believe it has taken so long to finish processing all that I captured over the autumn. The main holdup has been putting together a dark library that matches the temperatures at the star party which approached freezing both nights. Cameras with unregulated temperatures are a drag! At the moment I am sitting on over 30 hours of exposure time on four other objects waiting to be worked on. Anyhow, here is one down!

Capturing this nebula was a spontaneous decision at the star party once my primary targets had descended too low. I am glad I devoted two nights to this object because it is one of the more dramatic scenes I have encountered so far. The contrasting colors between the reflection nebula and H-alpha emission are wonderful. One of these days I would like to try a four panel mosaic to capture the H-alpha tail, but I will settle with this for today.

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Processing Workflow (PixInsight)
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1. Initial crop (Dynamic crop) .
2. Reduce light pollution gradients (DynamicBackgroundExtraction, subtract)
3. Neutralize background (BackgroundNeutralization).
4. Set white balance (ColorCalibration; use entire image including galaxy).
5. Set luminance coefficients to 0.333333 for RGB channels (RGBWorkingSpace).
6. Deconvolution with luminance mask.
7. Reduce background noise (TGVDenoise with inverted luminance mask).
8. Reduce background luminance noise (MultiscaleMedianTransform to Luminance with inverted mask)
9. Reduce background chrominance noise (MultiscaleMedianTransform to Chrominance with inverted lightness mask)
10. Non-linear stretch (HistogramTransformation, lower midtones slider aggressively).
11. Lower blackpoint (HistogramTransformation, raise blackpoint slider).
12. Lower blackpoint a little more (HistogramTransformation, raise blackpoint slider).
13. Restore colors and smooth star profiles to the heavily stretched stars using the method described by Vincent Peris (see Peris reference below).
14. Reduce green (SCNR to green, 90%).
15. Contrast curve to accentuate brightness differences in nebula (CurvesTransformation).
16. Enhance nebula contrast some more (LocalHistogramEqualization with mask selecting nebula only; kernal radius 162, contrast limit 1.2, amount 1.0, histogram resolution 10-bit, deselect circular kernal to help reduce ringing).
17. Reduce noise. The noise was mainly a smattering of brighter pixels that Manfred Shrwartz’ RemoveHotPixel process cleaned right up (Pixel Math [Shwartz script])
18. Increase color in star cores by duplicating image, blurring duplicate with convolution, increasing color saturation of duplicate with CurvesTransformation and then blending duplicate with original image through a star mask using the PixelMath expression = $T*.5 + blurredImage*.5.
19. Reduce star sizes (MorphologicalTransformation with mask selecting small stars; morphological selection, iterations 3, amount 0.3, selection 0.15, size 7 diamond structuring element).
20. Increase nebula color saturation, applied twice (CurvesTransformation to Saturation with luminance mask selecting nebula only).
21. Increase star color saturation (CurvesTransformation to Saturation with luminance mask selecting stars).
22. Tweak histogram to balance RGB of background since SCNR always seems to leave my backgrounds with an orangish cast (HistogramTransformation; raise blackpoint slider on each R, G, B channel individually until median of small preview containing only the background has equal R,G, and B values).
23. Sharpen nebula (MultscaleMedianTransform to Lightness, with luminance mask selecting nebula only; add bias to layers 4 [+0.01] and 5 [+0.04] ).
24. Reduce background brightness to median value of 0.1 (CurvesTransformation and blackpoint in HistogramTransformation).
25. Final crop to 5 x 7 aspect ratio (DynamicCrop)
26. Set ICC profile to sRGB for web publishing (ICCProfileTransformation).

References:

“M42 PixInsight Tutorial” by David Ault
http://trappedphotons.com/blog/?p=642

“Dynamic Range and Local Contrast” software tutorial by Vincent Peris:
http://pixinsight.com/tutorials/NGC7023-HDR/index.html

Manfred Schwarz’ galaxy tutorial:
http://www.astrophoto.at/PixInsight/

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Author

Jason Tackett
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Flaming Star Nebula in Auriga, Jason Tackett

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