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Contains:  M 16, Eagle nebula, NGC 6611
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The Eagle Nebula (M16) imaged in SHO, 





    
        

            Andrew Klinger
The Eagle Nebula (M16) imaged in SHO

The Eagle Nebula (M16) imaged in SHO

Technical card

Resolution: 3595x2684

Dates:May 12, 2018Aug. 2, 2018

Frames:
Astrodon Ha 5nm: 160x300" (gain: 200.00) -10C bin 1x1
Astrodon OIII 3nm: 37x600" (gain: 200.00) -10C bin 1x1
Astrodon SII 3nm: 36x600" (gain: 200.00) -10C bin 1x1

Integration: 25.5 hours

Darks: ~64

Flats: ~30

Bias: ~200

Avg. Moon age: 23.13 days

Avg. Moon phase: 41.92%

Bortle Dark-Sky Scale: 4.33

Astrometry.net job: 2276700

RA center: 275.081 degrees

DEC center: -14.224 degrees

Pixel scale: 2.527 arcsec/pixel

Orientation: 342.693 degrees

Field radius: 1.574 degrees

Locations: Atoka dark site, Atoka, Oklahoma, United States; Backyard, Flower Mound, Texas, United States

Data source: Backyard

Description

Here is my completed image of the Eagle Nebula (M16) imaged with Sulphur, Hydrogen, and Oxygen narrowband filters. This false-color widefield image of the nebula represents the strong oxygen signal as cyan, hydrogen as yellow/orange, and the stronger sulphur signal as red. Naturally, this nebula is nearly all red in color, as hydrogen-alpha dominates the field. With selective filters and processing I have stretched the intensity of the Oiii and Sii to better represent where they lie in the nebula.

Equipment:
OTA: William Optics GT81 w/0.8x reducer (382mm fl at f/4.7)
Mount: Orion Sirius EQ-G (HEQ-5)
Guidescope: Orion 50mm guidescope
Guiding camera: Orion StarShoot Autoguider
Imaging camera: ZWO ASI1600MM-Cool

Accessories:
DeepSkyDad Autofocuser
QHYCCD PoleMaster

Software:
SGP
PHD2
CdC
PixInsight

Acquisition:
Location: Flower Mound, TX for Ha(Bortle 7), Atoka, OK and Ft. Griffin State Historic Park, TX for Oiii and Sii(Bortle 3)
Dates: 5/12/18, 5/26/18, 5/27/18, 6/29/18, 6/30/18, 8/2/18, 8/3/18, 8/6/18
Gain: 200 Offset: 50
Camera temp: -10C
Sii: 36x600" Astrodon 3nm
Ha: 160x300" Astrodon 5nm
Oiii: 37x600" Astrodon 3nm
Total integration time: 25hr 30min
64x darks per calibration (master from library)
30x flats per calibration
200x bias per calibration (master from library)

Preprocessing:
Batch PreProcessing script to generate calibrated images
StarAlignment
LocalNormalization
ImageIntegration
DrizzleIntegration
DynamicCrop each master
DBE each master

Luminance Processing:
Duplicated the master Ha to use as the luminance
Deconvolution
TGV & MMT noise reduction (via Jon Rista's method)
HistogramTransformation bring to non-linear
Duplicated the image to create a starless version, using a starmask and several iterations of MMT and MT. Then pushed the faint nebulosity in the starless version using PixelMath expression: "1-(1-$T)*(1-$T)"
Combined the starless version with the image using PixelMath expression "F=0.4; (1-(1-$T)*(1-s)*F)+($T*~F)" followed by the same function but with F=0.2, (s=starless photo).
HDRMultiscaleTransform to reveal core
MultiscaleLinearTransform for sharpening
LocalHistogramEqualization
MMT and MT for star size reduction
MMT for noise reduction of the darker areas

Preparing separate Sii, Ha, and Oiii linear masters for tonemapping (applied to each master individually):
TGV & MMT noise reduction (via Jon Rista's method)
Removed stars via a StarMask and a few iterations of MMT and MT
Further removed background artifacts with an unmasked MMT
HistogramTransformation to bring to non-linear
HDRMultiscaleTransform to reveal core

Combined prepared Sii, Ha, and Oiii masters with ChannelCombination:
R: Sii
G: Ha
B: Oiii

Tonemap Processing:
Invert>SCNR green>Invert to remove magenta
Several a/b channel CurvesTransformations using ColorMasks to alter the colors to an aesthetically pleasing palette
CurvesTransformation for saturation
DBE to remove color bias in the corners

Combined Tonemap with Luminance using LRGBCombination
HistogramTransformation to stretch image slightly
UnsharpMask with a StarMask to harden up the soft stars a tad
CurvesTransformation for slight saturation
ACDNR for final noise reduction
Resampled to 40% for web posting

Comments

Author

ak_astro
Andrew Klinger
License: None (All rights reserved)
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The Eagle Nebula (M16) imaged in SHO, 





    
        

            Andrew Klinger

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Narrowband imaging