Daily Archives: January 31, 2015

M7, Ptolemy Cluster



Messier 7 or M7, also designated NGC 6475 and sometimes known as the Ptolemy Cluster, is an open cluster of stars in theconstellation of Scorpius. The cluster is easily detectable with the naked eye, close to the “stinger” of Scorpius (also called Scorpion). With a declination of -34.8°, it is the southernmost Messier object.

M7 has been known since antiquity; it was first recorded by the 1st-century Greek-Roman astronomer Ptolemy, who described it as a nebula in 130 AD. Italian astronomer Giovanni Batista Hodierna observed it before 1654 and counted 30 stars in it. In 1764, French astronomer Charles Messier catalogued the cluster as the seventh member in his list of comet-like objects. English astronomer John Herschel described it as “coarsely scattered clusters of stars”.

Imaging telescopes or lenses: Planewave Instruments 17″ CDK
Resolution: 2928×2915
Dates: Oct. 12, 2014
Frames: 24×120″
Integration: 0.8 hours
Avg. Moon age: 18.55 days
Avg. Moon phase: 84.67%
RA center: 268.453 degrees
DEC center: -34.805 degrees
Orientation: 178.704 degrees
Field radius: 0.634 degrees
Locations: Siding Spring Observatory (SSO), Coonabarabran, Australia
Author: Thomas