Open star clusters are widely distributed in our galaxy and represent a loose collection of stars which number from a few dozen to a few hundred stars and are weakly-held gravitationally. Perhaps the three most famous such open clusters are the Pleiades (M45) in Taurus, the Beehive (M44) in Cancer and the double cluster in Perseus. They are all characterized with a handful of hot and white prominent stars and nebular material surrounding these stars.

Note: Open cluster IC 4756 in Serpens depicted below is a rich open cluster comprised of about 100 member stars which are of varying brightness and is well detached from the background sky. The cluster spans 40 arc-minutes in diameter, lies at a distance of approximately 1,578 light-years away while spanning 15.2 light-years across and is dated at about 500 million years-old. The cluster is best observed using low magnifications (50-100x) during mid-summer as it approaches the southern meridian near midnight. IC 4756 was discovered by Harvard astronomer Solon I. Bailey while studying plates taken by a remote station in Peru. The cluster was also discovered independently by K. Graff in 1922 and which now bears his name.

Note: The image below was taken through thick humidity and will require a repeat visit.