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Contains:  Cone nebula, Christmas Tree cluster, NGC 2264, Horsehead nebula, IC 434, NGC 1990, M 42, Great Nebula in Orion, NGC 1976, Witch Head nebula, IC 2118, The star ιOri, The star Cursa (βEri), The star Mintaka (δOri), The star Saiph (κOri), The star Alnitak (ζOri), The star Alhena (γGem), The star Alnilam (εOri), The star Bellatrix (γOri), The star Betelgeuse (αOri), The star Rigel (βOri), Part of the constellation Orion (Ori), Part of the constellation Lepus (Lep), Part of the constellation Monoceros (Mon), Part of the constellation Eridanus (Eri)
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The Orion Molecular Cloud Complex presented in SHO

Technical card

Resolution: 3154x2697

Dates:Jan. 4, 2019Jan. 27, 2019Feb. 7, 2019

Frames:
Ha 5nm: 42x600" (gain: 200.00) -20C bin 1x1
Astrodon OIII 3nm: 43x600" (gain: 200.00) -20C bin 1x1
Astrodon SII 3nm: 53x600" (gain: 200.00) -20C bin 1x1

Integration: 23.0 hours

Darks: ~64

Flats: ~30

Bias: ~200

Avg. Moon age: 17.39 days

Avg. Moon phase: 20.89%

Bortle Dark-Sky Scale: 3.00

Astrometry.net job: 2849757

RA center: 86.536 degrees

DEC center: 1.168 degrees

Pixel scale: 38.938 arcsec/pixel

Orientation: 92.667 degrees

Field radius: 22.444 degrees

Locations: Atoka dark site, Atoka, Oklahoma, United States

Data source: Traveller

Description

My Winter project shows the Sulfur, Hydrogen, and Oxygen emissions in and around the Orion constellation in a very widefield view. In this false-color modified "Hubble-pallet" I show the Sulfur and Hydrogen emissions as the warm red-orange colors and the Oxygen emissions as Blue. As a bonus, towards the bottom of the image you can see the Rosette and Cone Nebula pair in the constellation Monoceros.

In the Winter months, Even in the brightest cities, you can make out the large rectangle constellation of Orion with the 3 belt stars down the middle. In my image you can see the bright red star Betelgeuse at the bottom-left of the rectangle. If you can imagine just how large the Orion constellation appears to your naked eye you can see the sky is most certainly not empty! Some of the most popular nebula reside in this constellation, try to find the Orion Nebula (M42) and The Horsehead Nebula (IC434) sitting within all the dust.

When I was thinking of a target to shoot this last Winter, I really wanted to pair a widefield lens with my astronomy camera to capture the rich Hydrogen emissions around Orion. This is not new and has been done many times, usually in the form of HaRGB (using a Hydrogen-alpha filter to enhance a natural color image). A thought came to my mind that what if we were much further away from Barnard's Loop (the smile-shaped nebula) and were imaging it in narrowband. When imaging in narrowband, most nebula have strong Ha signal, moderate Sii signal, and faint diffuse Oiii signal. This combination creates those rainbow-esque images you often see from the Hubble scope. So where there is strong Ha signal, Sii typically follows, and I was puzzled why I could not find any examples of a wide narrowband view of Barnard's Loop. So after capturing plenty of Ha data I tried for some Sii exposures and to my surprise the signal was quite strong and showing up in a single exposure! So from that exposure I committed to going full SHO on Orion.

Now here is where it gets interesting (or maybe not). Oiii emissions were expected around M42, The Horsehead, and Rosette Nebula, were a pleasant surprise on the "head" of Orion (SH2-264), but completely unexpected as a large-scale diffuse signal around Barnard's Loop. With a discerning eye you can see in the individual Oiii channel a very diffuse background glow extending around and below Barnard's Loop. I know from my data that it was signal well above the noise floor, but I cannot say for certain that it is in fact diffuse Oxygen emissions until someone else goes after this widefield view with the same results.

View "Revisions" for channel examples:
A: SHO
B: SII
C: Ha
D: OIII
E: Ha - starless

Equipment:
Lens: Rokinon 24mm f/1.4 (stopped to f/4)
Mount: Orion Sirius EQ-G (HEQ-5)
No autoguiding used
Imaging camera: ZWO ASI1600MM-Cool

Accessories:
QHYCCD PoleMaster

Software:
SGP
PHD2
CdC
StarNet
PixInsight

Acquisition:
Location: Atoka, OK (Bortle 3)
Dates: 1/4/19, 1/5/19, 1/27/19, 1/30/19, 2/7/19, 3/5/19
Gain: 200 Offset: 50
Camera temp: -20C
Sii: 53x600" Astrodon 3nm
Ha: 42x600" Astrodon 5nm
Oiii: 43x600" Astrodon 3nm
Total integration time: 23hr
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

Created a starless version of each channel using StarNet for use later in processing:
TGV & MMT noise reduction (via Jon Rista's method)
ArcSinhStretch x3
HistogramTransformation
StarNet

Luminance Processing:
Duplicated the master Ha to use as the luminance
TGV & MMT noise reduction (via Jon Rista's method)
ArcsinhStretch x3
HistogramTransformation
HDRMultiscaleTransform to restore M42 and Rosette
Combined the starless Ha image with the luminance using PixelMath expression "F=0.4; (1-(1-$T)*(1-s)*F)+($T*~F)" (s=starless photo).
Very small amounts of MMT noise reduction
HistogramTransformation
UnsharpMask
HDRMultiscaleTransform to reveal overblown parts of Barnard's Loop

Preparing the separate Sii, Ha, and Oiii starless images for tonemapping (applied to each master individually):
HDRMultiscaleTransform to reveal M42 and Rosette
HistogramTransformation

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 channels to an aesthetically pleasing palette
MMT for slight noise reduction

Combined Tonemap with Luminance using LRGBCombination
CurvesTransformation for slight contrast
CurvesTransformation saturation
MorphologicalTransformation for star size reduction
Resampled to 40% for web posting

Comments

Author

ak_astro
Andrew Klinger
License: None (All rights reserved)
260134
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Revisions

B

SII

C

Ha

D

OIII

E

Ha - starless

F

SHO v2 - Reprocessed the image as to not have black blotches and posterization in the low signal areas.

Sky plot

Sky plot

Histogram

The Orion Molecular Cloud Complex presented in SHO, 





    
        

            Andrew Klinger

In these public groups

Narrowband imaging