M81: Spiral Galaxy in Ursa Major



Object Data

Object type: Spiral Galaxy
Size: 90,000 light years diameter; 27 x 14 arc min
Magnitude: 6.4
Constellation: Ursa Major
Distance: 11.6 million light years

The spiral arms contain young hot bluish stars formed in the past few million years, while the core contains older red stars.  UV light from the hot stars is flourescing the surrounding clouds of hydrogen gas in the spiral arms giving off the red colors.

Exposure Data

Date: 11/4 and 11/5/21
Location: Little Blair Valley, Anza Borrego Desert, CA
Telescope: DSI RC10c.  1867 mm fl at f/7.3
Camera: FLI 6303E CCD camera with Astrodon Ha (3nm) and LRGB filters
Mount: AP 1100 mount GTOCP3
Exposure time: Lum (16 x 10min); RGB (8 x 5 min each); Ha (10 x 15 min)
Exposure time total: 6 hrs 50 min
An Ha layer was added to the LRGB layer to bring out the abundant hydrogen gas in the spiral arms of this galaxy

FOV = 37.4 x 29.8 arc minutes  (cropped from original)



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