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Catalogue and alternative designations NGC 6231


Type Open Cluster 
Position  16 54.0, -41 48
Constellation Scorpius
Camera and Telescope STXL16200 and 36.8cm Ritchey Chretien
Focal Ratio F9
Exposure Details LRGB with L=120m (incorporating synthetic luminance) and R = G = B = 70m all unbinned with Astrodon series 2 filters
Description Possibly one of the best open clusters in the sky, NGC 6231 is easily visible in binoculars and under very dark skies can be glimpsed without optical aid.  It was discovered by Giovanni Batista Hodierna before 1654 and independently by other subsequent astronomers including Lacaille.  NGC 6231 is part of the Scorpius OB1 association and is estimated to be about 3.2 million years old.