Hemisphere:  Southern  ·  Constellation: Orion (Ori)  ·  Contains:  41 the01 Ori  ·  42 c Ori  ·  43 the02 Ori  ·  44 iot Ori  ·  45 Ori  ·  De Mairan's nebula  ·  Great Orion Nebula  ·  Hatysa  ·  Lower Sword  ·  M 42  ·  M 43  ·  M43  ·  Mairan's Nebula  ·  NGC 1973  ·  NGC 1975  ·  NGC 1976  ·  NGC 1977  ·  NGC 1980  ·  NGC 1981  ·  NGC 1982  ·  NGC1973  ·  NGC1975  ·  NGC1977  ·  NGC1980  ·  NGC1981  ·  Orion Nebula  ·  Sh2-279  ·  Sh2-281  ·  The star 42Ori  ·  The star 45Ori  ·  And 6 more.
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Orion Nebula M42 under a full moon, 



    
        

            matthew.maclean
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Orion Nebula M42 under a full moon

Imaging telescopes or lenses: William Optics GT81

Imaging cameras: Altair Astro Hypercam 26C TEC

Mounts: iOptron CEM25p

Guiding cameras: Altair Astro GPCAM2 290M

Focal reducers: William Optics Flat 6Aiii

Software: Aries Productions Astro Pixel Precessor  ·  Astrosharp LTD Sharpcap 3.2 pro  ·  PixInsight 1.8  ·  GIMP

Filters: SkyTech L-pro max 2"

Accessory: William Optics Right Angle Guide Scope 50mm


Dates:Feb. 12, 2021Feb. 26, 2021

Frames:
SkyTech L-pro max 2": 48x120" (gain: 301.00) -10C
SkyTech L-pro max 2": 24x30" (gain: 301.00) -10C
SkyTech L-pro max 2": 24x4" (gain: 301.00) -10C

Integration: 1.8 hours

Darks: ~24

Bias: ~32

Avg. Moon age: 7.28 days

Avg. Moon phase: 49.81%

Bortle Dark-Sky Scale: 8.00

Temperature: -7.33


Astrometry.net job: 4272451

RA center: 5h 34' 50"

DEC center: -5° 17' 29"

Pixel scale: 2.017 arcsec/pixel

Orientation: -90.778 degrees

Field radius: 1.081 degrees


Resolution: 3100x2300

Data source: Backyard

Description

I managed to collect about two hours on I think the night before the full moon (only 99.8% illuminated!) since clear sky time is so hard to find this winter. If it had been anything other than the Orion nebula, I probably wouldn't have bothered, but I gave it a try with my L-Pro filter. In summer, I was measuring (SQM) about 18.5 mag/arcsec2 (~Bortle 7) and I have verified that snow cover does indeed make it worse; this winter, even with no moonlight, I have been getting around 17.5 (~Bortle 8). With the nearly full moon, I didn't even bother with a reading, but it was bad.

Still, for only two hours of capture, I got something nice. My main goal with this image project was to use some short-exposures I had collected two weeks before to control the brightness of the core and the Trapezium. My small refractor setup has a resolution of 2 arcsec/pixel, which gives me about 10 pixels of spacing corner-to-corner between the four Trapezium stars (as computed by their Dec and RA positions). So, resolution is crude, but the four (A,B,C,D) are individually resolvable and I am quite satisfied that I managed to preserve them in my final image.

With only two hours in the bright skies, all the noise in the background was the toughest thing. I had to really darken the background more than I would have preferred. Really, more integration time is needed, but it's what I have, and I learned a lot more about PixInsight trying to mask off the dim areas and smooth the background out. It's a little over-smoothed maybe, but I think it's the best compromise I could manage.

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Orion Nebula M42 under a full moon, 



    
        

            matthew.maclean