The Horsehead Nebula and Neighbors

All Images Copyright Steve Cannistra

Please click here for a composite image between this Canon 10 image and my Ha Horsehead image used as luminosity layer.

Magnitude:  Unknown
Distance: 1600 light years (Horsehead Nebula, aka B33); 826 light years (Alnitak- Zeta Orionis); 1165 light years (Sigma Orionis)
RA: 5h 40m 56s
Dec: -1 degrees 56' 21"

This is one of the most interesting regions of the night sky, containing 3 different types of nebulae:  emission, reflection, and dark.  The Horsehead Nebula itself, also known as Barnard 33 (B33), is part of an enormous dust cloud that extends to the left and downward in this photo, obscuring light from behind (notice the relative lack of stars in the lower half of the image).  Red light from IC434, the large emission nebula coursing diagonally through the field, is partially obscured by the Horsehead itself.  IC434 is actually part of a large gasseous region in Orion, extending towards and involving the Great Orion Nebula (M42).  If your monitor is adjusted correctly, you will be able to make out some of the faint nebulosity from this region, extending upwards and to the right of the field, heading towards M42.  To the upper right of the Horsehead at 1 o'clock is the bright star Sigma Orionis, which is responsible for producing the UV radiation that excites hydrogen atoms in IC434 to emit in the red.  To the left of the Horsehead at about 9 o'clock is the large Flame Nebula, aka NGC2024 or Orion B.  This is also an emission nebula, although the stars reponsible for its glow are buried deep inside and are not visible.  Notice the dark lanes or "veins" within the Flame, which are thought to represent an extension of the same dark nebula responsible for creating the Horsehead.  The brightest star in this region is Alnitak, aka Zeta Orionis, and created an enormous amount of interference in my unprocessed image that obscured the uppermost region of the Flame.  Alnitak forms the left hand portion of Orion's belt and is much closer to us than either the Horsehead, IC434, or NGC2024 (and it is therefore not responsible for illuminating any of the other objects in the field).  Finally, there are several beautiful blue reflection nebulae in this image, visible because they are in the foreground of the dark nebula itself. These reflection nebulae are IC435 in the lowermost portion of the image, NGC2023 to the immediate left of the Horsehead, IC432 to the upper left of the Flame, and IC431 just above IC432.  
Please click here for a higher resolution image of this region.

Photographic Details:

Date:  November 23, 2003- early morning.
Scope:  Takahashi Sky 90 at f4.5 with field flattener/focal reducer, piggybacked on LX90 (which is mounted on a Meade Superwedge).
Autoguider:  STV with e-finder.
Camera:  Canon 10D.
Filter:  IDAS LPS.
Exposures:  15 x 5' at ISO 1600, for a total exposure time of 75 minutes.
Conditions:  Temperature 35 degrees F; below average transparency; average seeing; very dewy; calm.
Raw conversion, adaptive dark frame calibration, alignment, min/max excluded averaging done in ImagesPlus; Background compensation to correct for mild vignetting also performed in ImagesPlus and worked extremely well for this image.  Levels, curves, and layer mask adjustments in Photoshop. Alnitak was extremely bright in the original image and obscured part of the Flame, requiring several curves adjustments of this region to enhance the topmost portion of the Flame.  As a result, I could not capture as much of the Flame as I had hoped- this will require another session using a shorter exposure time, which I will eventually feather into the current image.  This was one of three images shot during this session (the first two being the Pleiades widefield and the Rosette, which started in the late evening on 11/22/03).

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