Orion region

On this page a 24°×34° wide-field view of the constellation Orion is presented in different color composites. This region is full of emission nebulae and Molecular clouds.

The pictures below are downscaled versions. Full resolution images with more than 100 megapixels can be loaded with a Javascript viewer by clicking on the images in the first section. Selected details are shown in the second section. The third section presents some discoveries. Image and instrument data can be found at the end of this page.

Full views

Click on the images to load a full resolution version with more than 100 megapixels using a JavaScript viewer.

Orion region in H-alpha, blue continuum and red continuum
This image is a false color composite in which H-alpha (including red continuum) is mapped to red, blue continuum (including [OIII] and H-beta emissions) is mapped to green, and red continuum (without H-alpha) is mapped to blue. Reflection nebulae appear green to blue, while HII regions are red. Stars in the continuum channels are partially subtracted to make the faint nebulae visible.

Orion region in H-alpha
Legend for false color image of orion region in H-alpha
This visualization is a pseudo-color image that only uses the H-alpha data (including some red continuum). It shows many more details of the emission nebulae than the image above.
Color composition: After partial star subtraction, the dynamic range was compressed using a non-linear high-pass filter. This results in a compression ratio r, which is used to calculate the color as depicted in the legend. (The legend shows the compression c:=1-r). Blue regions are compressed the least, while white regions are compressed the most. Luminance is determined by the tonal curve-corrected result of the dynamic range compression.

Orion region in RGB
An almost-true color image. Unlike to the other images, the stars are not subtracted. This improves the visibility of dark nebulae that absorb the light from the stars behind.
Due to the limited resolution of continuum channels, the image is only presented at half resolution.

Selected details

Here are a few details that also can be seen using the JavaScript viewer.
Orion region: M42, Running Man Nebula, Horsehead Nebula, Flame Nebula
A region full of many kinds of nebulae. Most famous ones are (from top left to lower middle): NGC 2071 (cyan), Flame Nebula (pinkish, almost white), Horsehead Nebula (pink), Running Man Nebula (mostly cyan) and M42 (yellowish).
Orion region: Barnards loop and Witch Head Nebula
A wider view which also shows the Which Head Nebula (bottom right) Barnards Loop (the red arc across the whoole image).
Orion region: SH2 264
Orions head, SH2 264 in H-alpha.
Orion region: Detail of Barnards loop
A detail of Barnards Loop in H-alpha. Flame Nebula and Horsehead Nebula can be seen too.
Orion region: M42 region
The M42 region and a part of Barnards Loop in H-alpha.

Observations and discoveries

Click on the following links for presentations of interesting observations using the JavaScript Viewer. The views above show many nebulae that cannot be found in catalogs. (The JavaScript Viewer allows identifying objects using catalogs or SIMBAD and defining new objects.) Some (probably not all) of these unexplored nebulae have been collected in the list below. Click on the following links for a presentation. Notes

Image data

Images where captured with a camera array which is described on the instruments page.

Image data are:

Projection type: Stereographic
Center position: RA: 5h28, DEC: 1°
Orientation: North is up (exactly)
Scale: 10 arcsec/pixel (in center at full resolution)
FOV: 25°×34° (through center)
Exposure times: H-alpha: 7.7d, continuum channels: 4.3d (sum of exposure times of all frames used to calculate the image)

Image processing

All image processing steps are deterministic, i.e. there was no manual retouching or any other kind of non-reproducible adjustment. The software which was used can be downloaded here.

Image processing steps where:

  1. H-alpha only: bias correction, photon counting
  2. Dark current subtraction, flatfield correction, noise estimation
  3. Alignment and brightness calibration using stars from PPMXL catalog
  4. Stacking with masking unlikely values and background correction
  5. Extracting stars
  6. Denoising and deconvolution both components (stars and residual)
  7. RGB-composition (same factor for stars and residual for the true color composite)
  8. Dynamic range compression using non-linear high-pass filter (except of the true color composite)
  9. Tonal curve correction


  1. Bram B. Ochsendorf and Anthony G. A. Brown and John Bally and Alexander G. G. M. Tielens, 2015, Nested shells reveal the rejuvenation of the Orion-Eridanus superbubble.
  2. The Orion Molecular Cloud, seen by IRIS+CO map.

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