The Great Nebula in Orion (M42) and NGC 1977 (Running Man Nebula)

All Images Copyright Steve Cannistra

Please click here or on image for a higher resolution vertical view (693 x 1375).
Please click here for the highest resolution vertical view (990 x 1964).
Please click here for a higher resolution horizontal view (1375 x 693).
Please click here for the highest resolution horizontal view (1964 x 990).

Magnitude:  5.0
Size: about 1.5 degrees (for the final mosaic)
Distance: 1600 light years
RA: 5h 35m
Dec: minus 5 degrees 35' 54"

This is my latest image of the M42 complex, representing a two frame mosaic and about 6.5 hours of exposure time.  The Great Orion Nebula is the brightest nebula visible to the naked eye, forming the middle part of the Hunter's sword in the famous constellation Orion.   It is a breathtaking view in even small telescopes, where tendrils of gas can be appreciated even without the aid of special filters.  The use of a UHC filter improves contrast significantly and reveals a significant amount of faint nebulosity during visual observation.  The typical visual view in a telescope is pale white to faint green, due to the human eye's poor color response to low light (especially in the red, which is emitted by this nebula due to excitation of hydrogen gas as a result of radiation from newly formed stars).  In this view, The Great Orion Nebula (M42) is on the right, de Mairan's Nebula (M43) is just below center, and the Running Man Nebula (NGC 1977) is on the left, a beautiful reflection nebula that derives its blue color from reflected light of nearby stars.  Please be sure to check out the links under the photo for higher resolution views.

Photographic Details:

Date:  December 15 and
December 17, 2004.
Scope:  Takahashi Sky 90 at f4.5 with field flattener/focal reducer, on a Losmandy G11 mount.
Autoguider:  STV with e-finder.
Camera:  SXV-H9.
Filters:  Ha (13nm bandpass), L, R, G, B type II filter set, all from Astronomik.
Exposures (all unbinned):  December 15 (the right hand side of the mosaic):  22 x 4' luminance; 20 x 30" luminance; 6 x 4' each R, G, B; 20 x 30" each R, G, B;  6 x 5' Ha; 20 x 30" Ha.  December 17 (the left hand side of the mosaic): 
20 x 4' luminance; 6 x 4' each R and G, 8 x 4' B.  Total exposure time about 6.5 hours.
Conditions:  In a word- glorious (except for the temperature, which was 18-20 degrees F on both nights).  I've never had transparency and seeing conditions like this.  No clouds. No wind. 
After the moon set, the sky was inky black, and the stars hardly twinkled....
Post-processing:  LHa:(LHa:R:G:B)- please see below for details.  No darks, flats, or bias frames required.  Alignment, combining (min/max excluded averaging), and DDP done in ImagesPlus.  Levels, curves, and layer mask adjustments in Photoshop.  Processing this image required several techniques, which were straightforward but time consuming.  These included:  1) Making layer masks using the shorter 20 x 30" luminance, RGB, and Ha exposures for the Trapezium region.  The 30" Ha exposures were needed to provide good definition of the Trapezium itself;  2) Sharpening using a combination of high pass filtering (radius of only 2 pixels, using Overlay mode in PS) and unsharp masking (amount 80% and radius 1.5) applied selectively to certain regions.  The image was quite smooth and permitted sharpening without introducing too much noise;  3) The luminance channel was comprised of L plus Ha, restricting the Ha contribution to about 50% opacity.  This LHa luminance component was combined with the RGB in Photoshop as a standard luminosity layer (i.e., I did not use the technique of Luminance Correction for this image, since there was reasonably good matching between luminance signal and color).  After boosting the color saturation of the RGB component, a mild guassian blur was applied to the color layer, the image was flattened (now representing an LHa:R:G:B layer), and it was then used as color for another LHa luminance channel (this is a modification of a technique developed by Rob Gendler).  Thus, the final image is LHa:(LHa:R:G:B), which resulted in good preservation of detail and color;  4) Registration of the two frames was done in Registar, prior to mosaic construction.

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