Orion region

Images below show a 23°×34° wide field view of constellation Orion which is rich of nebulae. Descriptions can be found below the images. Image and instrument data can be found at the end of this page.

The pictures on this page are downscaled versions. Full resolution images with more than 100 megapixels can be loaded with a Javascript viewer by clicking on the images. If your browser crashes while attempting to load such images or in case of low bandwidth connections you can try the half resolution version. The link can be found below the image.

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 (31 MB): Javascript Viewer Direct download
Half resolution (8.4 MB): Javascript Viewer Direct download
 
This visualization is a false color image where H-alpha (including red continuum) is mapped to red, blue continuum is mapped to green and red continuum (without H-alpha) is mapped to blue, i.e. H-alpha emission nebulae are shown red 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 (34 MB): Javascript Viewer Direct download
Half resolution (7.3 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 then 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 values c:=1-r). The luminance is determined by the tonal curve corrected result of the dynamic range compression.

Orion region in RGB
Half resolution (10.4 MB): Javascript Viewer Direct download
 
This image comes close to a true color view. Red contains 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, because they cover the light from the stars behind.
 
The only image processing steps after color composition are dynamic range compression using a nonlinear hi-pass filter and tonal curve correction.
 
Due to the limited resolution of the continuum data that image is only presented at half resolution.

It should be noted that 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: Barnard 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: Detail of Barnard loop
A detail of Barnards Loop in H-alpha. Flame Nebula and Horsehead Nebula can be seen too.

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: 5h30, DEC: 1°
Orientation: North is up (exactly)
Scale: 10 arcsec/pixel (in center at full resolution)
Dimensions: 23°×34° (through center)
Exposure times: H-alpha: 7.4d, continuum channels: 5.7d (sum of exposure times of all frames used to calculate the image)

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