M 7 – NGC 6745


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The so called Ptolemy’s Cluster was already known to ancient Greeks. Ptolemy described it without doubt. It has been catalogued by many astronomers, including Charles messier, Edmund halley and Nicolas Louis de Lacaille. This is a large cluster, visible wuth the naked eye and located at about 1,000 light years. More than 80 stars belong to this cluster. Its brightest stars are HR 6658 (a double: 5.6-7.9), HR 6657 (also double: 6.1-6.9) and HR 6662 (variable: 6.0-7.3).

Additional Information


Name(s): M7, NGC 6745, Ptolemy’s Cluster

Type: Open Cluster

RA:  17h 53m 49.9s

Dec: -34º 46’ 54”

Constellation: Scorpius

Size (arcmin): 80×80

Magnitude: +3.3

Distance: 1,000


Date: 2014-08-22

Location: SSO near Coonabarabran, NSW Australia

Size (arcmin): 230×150

Telescope: Takahashi FSQ 106 f/5

Camera: SBIG STL-11000M (4008x2672pix)

Guiding: not recorded

Total exposure: 100 min (L: 25min; RGB: 75min)

Processing: PixInsight

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