Orion the Hunter, Widefield Composite

       Orion Widefield

All Images
Copyright Steve Cannistra

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Orion is perhaps the most famous and easily recognized constellation.  The large outline of the Hunter always comes up sideways, as nicely captured in a poem by Robert Frost.  Although this region contains many wonderful targets for high magnification imaging, it also has an air of stately winter beauty when viewed through a wide field.  Broad bands of emission nebulosity can be seen throughout the head and body of the hunter, with the region on the left referred to as Barnard's Loop.  The Horsehead and Orion Nebulae are also shown in this image.  Please see below for details regarding how this image was taken.

Photographic Details:

Dates:  December 3
, 2004- widefield view through the Canon 10D using the 17-40mm EF Canon L series lens at f5.6; December 3, 2004- Ha contribution through the SXV-H9 using a 28mm FD Canon lens at f5.6; February 7, 2004 and November 23, 2003- High resolution image of the Horsehead; October 30, 2003 and November 23, 2003- High resolution image of M42.
Camera and Lens:  As above.
Mount:  Losmandy G11.  No autoguiding was necessary for the 12/3/04 session in view of image scale.
Filter:  Astronomik 13nm bandpass Ha filter.
Exposures:  For December 3, 2004 images:
Canon 10D- 3 x 1', ISO 400 through 17-40mm EF Canon L series lens at f5.6.  SXV-H9- 8 x 3' unbinned Ha subexposures each, for two different fields (upper and lower regions of Orion, respectively), through the Canon 28mm lens at f5.6.  See above links for details regarding my other images used in this composite.  Total exposure time for all components was about 5 hours (including Horsehead and M42 images).
Conditions (12/3/04):  Temperature 28 degrees F; above average transparency; below average seeing; occasional breeze.

Post-processing:  No darks, flats, or bias frames used.  10D exposures were taken in raw format and converted in ImagesPlus.  Both 10D and SXV-H9 images were aligned, combined, and DDP stretched in ImagesPlus.  The Ha fields (i.e., the SXV-H9 images) were registered and merged using Registar, providing a nice stretch of red signal from the head of Orion down to the end of Barnard's loop.  This was then combined with the red channel of the 10D image using lighten mode in Photoshop.  Finally, the Horsehead and M42 images were registered and overlaid onto the 10D image, again using lighten mode.  This sounds straight-forward, but was actually a challenge, since several gradients and edges needed to be controlled during construction of the composite.  I purposefully chose short exposures for the 10D, so as to minimize contributions from background stars as well as light pollution.  I also attenuated the Ha contribution in the red channel (50% opacity in lighten mode), since I did not want this to overpower the image.  In the future, I will attempt to obtain signal for the Witch Head region using a luminance filter, which will then be combined with the blue channel of this image.

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