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The Double Cluster in Perseus

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About this observation
Observer
Graeme Coates
Time of observation
02/01/2020 - 11:03
Object
Double Cluster
Observing location
EEYE
Equipment
Skywatcher Esprit ED80
SBIG STF8300 camera
Exposure
5.9 Hrs combined LRGB
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Also known as h and χ Persei, the Double Cluster (comprising NGC 869 and NGC 884) is a "line of sight" pairing in the constellation in Perseus, though actually they are only a few hundred light years apart. The clusters have a combined visual magnitude of 3.7 and 3.8 and are visible to the naked eye as a fuzzy patch between Perseus and Cassiopeia.

NGC 869 has a mass of 3700 solar masses and NGC 884 2800 solar masses; so the total mass for the complex is estimated in excess of 20,000 solar masses when including an extensive halo of stars. Based on their individual stars, the clusters are relatively young, both 12.8 million years old, with the hottest stars having spectral class B0; NGC884 also has 5 prominent red supergiants including variable RS Per (closest to the centre of the lower cluster).  This excellent rendering of the famous double cluster gets top marks for sharpness and accurate processing.

Image acquisition: Graeme Coates & Paul Tribe
Processing: Graeme Coates

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