Open Cluster in Cygnus
Messier 39 is a large, coarse open cluster
of about 30 bright stars in a triangular shape, about 1000 light years
away. It occupies an area of sky
about the size of the full moon, and it can be seen with the naked eye as a dim
hazy patch about 10 degrees northeast of Deneb, the
brightest star in Cygnus. Through
binoculars, a dozen or so stars can be seen, and with a telescope at low power,
its blue-white stars shine brightly against the Milky Way background.
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Image details: Exposure times of 15 minutes each of luminance, red, green, and blue, taken with an SBIG ST-8300M imager and a 500-mm Tokina lens at f/8.
June 2017