Hemisphere:  Southern  ·  Constellation: Orion (Ori)  ·  Contains:  Great Nebula in Orion  ·  M 42  ·  M 43  ·  NGC 1976  ·  NGC 1982  ·  The star θ1Ori  ·  The star θ2Ori
M42 Orion Nebula LLRGB, 


            Barry Brook
M42 Orion Nebula LLRGB
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M42 Orion Nebula LLRGB

Technical card

Imaging telescopes or lenses: Orion ED80T CF

Imaging cameras: Orion StarShoot G3 Mono CCD

Mounts: Skywatcher AZ EQ-6 GT

Guiding cameras: ZWO optical ASI120MM-S

Focal reducers: TeleVue 0.8x Photo Reducer/Flattener TRF-2008

Software: Cartes du Ciel  ·  Nebulosity 3  ·  Stark Labs PHD2 v2.2.2g  ·  EQASCOM  ·  StarTools  ·  AstroTortilla 0.7

Filters: ZWO optical ZWO RGBL Filters

Accessory: Orion Thin Off-Axis Guider (TOAG)

Dates:Aug. 29, 2014

Frames: 70x30" 3C

Integration: 0.6 hours

Darks: ~50

Flats: ~100

Bias: ~100

Avg. Moon age: 3.55 days

Avg. Moon phase: 13.60%

Bortle Dark-Sky Scale: 6.00

Mean FWHM: 1.85

Temperature: 4.00

Basic astrometry details

Astrometry.net job: 355845

RA center: 5h 35' 16"

DEC center: -5° 23' 34"

Orientation: -178.774 degrees

Field radius: 0.598 degrees

Resolution: 620x479


The great nebula in Orion, taken just before first light on 29 August using an ED80T CF astrograph with an Orion Starshoot G3 mono CCD. My 'real AP' learning kit.

This is an experimental image, prior to my work on some objects with deep integration times (LRGB data collected, now acquiring some Ha for these).

Orion was low in the morning sky, and I only had less than 2 hours to capture all my data due to the balance of needing Orion to rise to a sufficient altitude, and to avoid the brightening astronomic dawn.

The image is composed of the following:
Lum = 18 x 30 sec + 23 x 10 sec
R, G & B = 15 x 30 sec for each channel

I then created a synthetic luminance channel using an exposure-based weighting of the L30, L10 and R, G and B luminances. The L and RGB chrominance channels were then processed separately before final combination.

All subs were unbinned (35 minutes total integration). Guided using PHD2 with an ASI120MM-S camera and an OAG.

Captured and pre-processed with flats (light box), bad pixel map and bias in Nebulosity. Post-processed in StarTools.

This camera/astrograph is heavily undersampled at 4.6 arcseconds per pixel (and the StarShoot G3 chip is small and yields relatively low resolution images, at 752 x 582 pixels). To overcome these constraints, I used drizzle alignment in Nebulosity (this brought it up to an equivalent 2.5 megapixel image). However, there is some graininess in the image due to a lack of sufficient subs, especially in the lower signal areas (outer regions).

But overall, I deem this experiment to have been a success.



  • M42 Orion Nebula LLRGB, 


            Barry Brook
  • Final
    M42 Orion Nebula LLRGB, 


            Barry Brook

Sky plot

Sky plot


M42 Orion Nebula LLRGB, 


            Barry Brook