Orion the Hunter, Widefield Composite
Description:
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.
Please
note: Graphics on this website may not be reproduced without
author permission.
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