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Technical card

Resolution: 3882x2556

Dates: March 1, 2014

Frames: CLS-CCD: 40x90" ISO1600

Integration: 1.0 hours

Darks: ~41

Bias: ~67

Avg. Moon age: 29.14 days

Avg. Moon phase: 0.17%

Astrometry.net job: 203914

RA center: 85.362 degrees

DEC center: -2.129 degrees

Pixel scale: 1.235 arcsec/pixel

Orientation: 115.688 degrees

Field radius: 0.797 degrees

Locations: York River State Park, Williamsburg, Virginia, United States

Description

One of the most awe-inspiring regions of the deep sky lies within the well known constellation Orion. The brightest star in the image is the left-most star of Orions’ belt, named Alnitak. To its left is the stunning Flame Nebula, a cloud of glowing hydrogen gas and light-absorbing dust which gives the emission nebula dark lanes. The expansive red curtain of light to the right of Alnitak is also an emission nebula where hydrogen atoms are excited by ultraviolet radiation from nearby stars and glow at near-infrared wavelengths. A cloud of strongly absorbing dust in the foreground forms the famous Horsehead Nebula due to its distinctive shape. The smaller blue cloud to the left of the Horsehead Nebula is a reflection nebula where dust has scattered light from nearby stars. These objects are all 900 - 1500 light years from Earth.

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Post-Processing Workflow (PixInsight)
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Credit for the workflow used to process this image goes to Kayron Mercieca and his excellent wide-field Orion LRGB post-processing tutorial. Thank you Kayron for sharing your expertise. Visit Kayron’s website for more details: http://lightvortexastronomy.blogspot.com.

While I followed his workflow quite rigidly, there are a few minor differences. I implemented banding reduction up front, reduced green chrominance noise with the SCNR tool at the tail end of processing instead of towards the beginning, targeted nebulosity for the the final contrast and brightness increases rather than the whole image and increased color saturation using CIE L*a*b curve transformations instead of saturation curve transformations.

1. Reduce banding (CanonBandingReduction)
2. Crop alignment artifacts (Dynamic Crop)
3. Reduce background gradients (Dynamic Background Extraction)
4. Neutralize background color (BackgroundNeutralization)
5. White balance (ColorCalibration)

Process luminance
6a. Extract luminance image from RGB (ChannelExtraction)
6b. Reduce background noise (ATrousWaveletTransform, MultiscaleMedianTransform)
6c. Non-linear stretch to increase dynamic range and contrast (HistogramTransformation)
6d. Reduce noise in strong signal areas (ATrousWaveletTransform, ACDNR)
6e. Lower black point slightly (HistogramTransformation)
6f. Enhance contrast of large scale features in weak signal areas (LocalHistogramEqualization)
6g. Enhance contrast for smaller scale features in strong signal areas (LocalHistogramEqualization)
6h. Sharpen strong signal features (ATrousWaveletTransform)

Process RGB
7a. Suppress background noise in RGB image (ATrousWaveletTransform, MultiscaleTransform)
7b. Non-linear stretch to increase dynamic range and contrast (HistogramTransformation)
7c. Reduce background noise (ATrousWaveletTransform, ACDNR)
7d. Reduce background chrominance noise (ATrousWaveletTransform)
7e. Lower black point slightly (HistogramTransformation)
7f. Blur RGB image (ATrousWaveletTransform)

8. Combine luminance and RGB images; saturate colors slightly and reduce chrominance noise (LRGBCombination)
9. Reduce green chrominance noise (SCNR)
10. Increase nebulosity contrast and brightness (CurvesTransformationTool)
11. Increase saturation and emission nebula IC 434 redness (CurvesTransformationTool; a and b channels of CIE L*a*b color space)

Comments

Author

Jason Tackett
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Sky plot

Sky plot

Histogram

Flame Nebula and Horsehead Nebula, Jason Tackett

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