Telescope: Unitron 155c 4” f/15
Camera: Canon EOS Ra, Interval Timer (no computer)
Filter: 2” GSO IR Cut Filter
Guide scope: None
Exposure: 32x1sec, ISO 800, saved as RAW
Darks: Internal (Long Exposure Noise Reduction)
Flats: None
Average Light Pollution: Bortle 8
Stacking: Mean with a 1-sigma clip.
White Balance: Nebulosity Automatic
Software: Backyard EOS, Deepsky Stacker, Nebulosity, Photoshop
Sigma Orionis is one of my favorite fields in the winter and spring sky. Sigma itself can be easily spotted with your unaided eye as a modest star just south of the easternmost star in Orion’s Belt; Alnitak. In a small telescope Sigma shows two nearby companions just off to the northeast as well as a wide pair off to the northwest (Struve 761). Close examination in a larger telescope shows a third companion to Sigma close by to the southwest, making Sigma a quadruple star system, and the southern star of the northwestern pair splits into a beautiful close pair of equal stars, making this a wonderful field of 7 closely arranged stars. (The brightest component of Sigma is actually a close binary system, making this a quintuple system!) During the winter months I always take a minute to stop by and to visit these old friends and I often use them to take a quick peek at the quality of the optics in a newly acquired telescope.
Sigma Orionis is currently well placed high in the southwest at dusk.
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