The Great Nebula in Hydrogen Alpha

M42 in Ha
All Images Copyright Steve Cannistra

Please click here for a medium size (35%).
Please click here for a large size (50%).
Please click here for the largest size (65%).

RA: 5h 35m 33s
Dec: minus 05 degrees 25' 29"
Position Angle: + 87 degrees
FOV: 4 x 3 degrees

The Great Orion Nebula (M42) is the large, bright, central structure in the above field of view.  M42 is a stellar nursery that forms 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).  As shown above, the use of a hydrogen alpha filter with a CCD camera permits capturing the full extent of surrounding faint emission nebulosity that permeates this region.  This image will ultimately be used in a new HaRGB composite, once I have time and clear skies to acquire the color data.  Please click here to learn more about M42.

Photographic Details:

Date:  December 29, 2007.
Scope:  Takahashi FSQ106 at f5 on the Takahashi NJP Mount.
Autoguider:  SBIG ST-402 with e-finder.
Camera:  STL11K -20C.

Baader 7nm Ha filter (50mm unmounted).
Exposures:  9 x 20', composited with 6 x 5' for trapezium region (which still could have used less exposure).  Total exposure 3.5 hours.
Conditions:  Temperature was approximately 35 degrees F over the course of the night (focusing every 40 minutes).
Post-processing:  Calibrated, aligned, and Sigma Clip combined in Maxim, followed by DDP in ImagesPlus (IP).  Further processing in Photoshop CS (16 bit format).
Please note:  Graphics on this website may not be reproduced without author permission.

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