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Contains:  Great Orion Nebula, IC 420, Lower Sword, M 42, M 43, Mairan's Nebula, NGC 1973, NGC 1975, NGC 1976, NGC 1977, NGC 1980, NGC 1981, NGC 1982, Orion Nebula, The star 42Ori, The star 45Ori, The star θ1Ori, The star θ2Ori, The star ιOri, Upper Sword, the Running Man Nebula
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The Great Orion Nebula in HOO, 


The Great Orion Nebula in HOO
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The Great Orion Nebula in HOO

Technical card

Imaging cameras: Nikon D5300 Full Spectrum Modified

Guiding telescopes or lenses: Agena Astro Guidescope, 50mm f/3.8, 190 mm focal length

Guiding cameras: ZWO ASI120MC-S

Focal reducers: William Optics Flat 6A II

Software: PixInsight 1.8

Filters: Optolong L-eNhance 2"

Dates:March 7, 2020

Frames: 82x360"

Integration: 8.2 hours

Avg. Moon age: 12.19 days

Avg. Moon phase: 92.70%

Basic astrometry details job: 3381489

RA center: 5h 35' 18"

DEC center: -5° 25' 30"

Pixel scale: 2.089 arcsec/pixel

Orientation: 6.412 degrees

Field radius: 1.830 degrees

Resolution: 3500x5249

Locations: Home, Silver Spring, Maryland, United States

Data source: Backyard


Every winter I look forward to the return of the great Orion nebula. This year I captured I tried a few different approaches. First I captured a wide field view of the central Orion constellation using a short telephoto lens (see: Second, I went for a longer exposure than last year with my APO refractor taking advantage of newly developed skills in guided imaging. I worked on this one on and off from November 2019 through March 2020, ending up with about 8 hours of 6 minute subs that I used in conjunction with a series of 60 s subs to generate the final HDR image. I like this much more than last years attempt at this focal length (See: This years version has much lower noise, better detail in the nebulocity, and I managed to capture the Trapezium with the improved HDR processing. This version of the image includes both the H-alpha data (red channel) and OIII data (green & blue channels) combined using the HOO palette.

Imaged with WO GT81 at F4.7 (382 mm focal length) using Flat6A II field flattener/0.8x reducer, Optolong L-Enhance dual narrowband filter, and full spectrum modified Nikon D5300.

Long exposures: Total integration time of ~8 hours using 82 subs at ISO400x360 sec.
Short exposures: Total integration time of ~0.5 hours using 30 subs at ISO400x60 sec.

Pre-processed using PixInsight Batch Pre-Processing (BPP) script. Images calibrated using darks, flats, and flat darks. Extracted red/green/blue channels using BatchChannelExtraction script. R and G+B channels registered and stacked using StarAlighment and Integration.

R and G+B channels individually post-processed in Pixinsight: Cropped, gradient removal with ABE, HDRComposition (binarizing threshold = 0.8) to combine different exposure lengths, MLT for noise reduction, stretched using masked stretch, Curves Transformation, TGVDenoise for noise reduction, HDR transform, Local histogram transform, morphological transform to shrink stars.

HOO image generated using SHO-AIP script with luminance using Ha data. Additional post-processing of the HOO image included photometric color calibration and color saturation adjustment.

For Ha version of the image and additional acquisition details, see:



License: None (All rights reserved)

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The Great Orion Nebula in HOO,