Orion region

On this page a 24°×34° wide-field view of the constellation Orion is presented. All 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 a second section Image and instrument data can be found at the end of this page.

There are short descriptions below each image.

Full views

Click on the images to load a full resolution version with up to more than 100 megapixels using a JavaScript viewer. If browser cannot handle this or in case of low bandwidth connections you can try the half resolution version. The links can be found below the images.

Some browsers (namely Gecko based ones like Firefox) cannot downscale properly with Javascript, they just downsample. This results in noisy images and randomly appearing and disappearing stars while zooming. If such artifacts appear you can try the direct download version and use the browsers built-in viewer. Download links can be found below the images.

Direct download is also recommended for mobile devices (and devices with touchscreen) because browsers for these devises usually have a integrated viewer which is faster than the Javascript viewer and can handle larger data.

Orion region in H-alpha (red), blue continuum (green) and red continuum (blue)
Full resolution (39 MB): Javascript Viewer Direct download
Half resolution (11 MB): Javascript Viewer Direct download
This visualization is a false color image where H-alpha (including red continuum) is mapped to red, blue continuum (including some emission lines like [OIII]) is mapped to green and red continuum (without H-alpha) is mapped to blue, i.e. H-alpha emission nebulae appear reddish and reflection nebulae appear blue to green.
Stars in the continuum channels are partially subtracted in order to make the faint reflection nebulae visible. Further image processing steps are dynamic range compression using a nonlinear hi-pass filter and tonal curve correction.

Orion region in H-alpha (false color)
Legend for false color image of orion region in H-alpha
Full resolution (36 MB): Javascript Viewer Direct download
Half resolution (9 MB): Javascript Viewer Direct download
This visualization is a false color image which only uses the H-alpha data (including some red continuum). It shows much more details of the emission nebulae than the image above.
After partial star subtraction the dynamic range was compressed using a non-linear hi-pass filter. That leads to a compression ratio r which is used to calculate the color as depicted in the legend. (The legend shows the compression c:=1-r). The luminance is determined by the tonal curve corrected result of the dynamic range compression.

Orion region in RGB
Half resolution (11 MB): Javascript Viewer Direct download
This image comes close to a true color view. Red component shows red continuum including some (but reduced) H-alpha, green continuum is mapped to green and blue continuum is mapped to blue.
Unlike to the other images the stars are not subtracted. This makes the dark nebulae visible which cover the light from the stars behind.
The only image processing step after color composition was a tonal curve correction (no dynamic range compression).
Due to limited resolution in continuum channels the image is only presented at half resolution.

All image processing steps are deterministic, i.e. there is no manual retouching or any kind of non-reproducible adjustment.

Selected details

Here are a few details that also can be seen using the Javascript viewers (if browser works correctly).
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: Lambda Orionis Ring (SH2-264)
Orions head, the Lambda Orionis Ring (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.
Orion region: M42 region
Two well known bubbles are easily visible in H-Alpha: Barnards loop (cyan) and the Lambda Orionis Ring (yellow), see [1]. (The ring structures are projections of spherical shells. The bubble around λ-Ori can be seen as a ring in infrared, see [2].) There seems to be a third bubble (white) which is very faint but forms a perfect circle (or sphere) and maybe even a fourth one (grey).

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: 7.5d, 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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