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: The open cluster NGC 6823 in the constellation of Vulpecula is an impressive collection of 50 to 100 stars with a concentration towards the core involving the brighter member stars which range in magnitude between 9.5 and 11. NGC 6823 lies within an area which is characterized with a lot of emission nebulosity, classified as NGC 6820, and which includes impressive dark lanes. With an apparent diameter of approximately 10 arc-minutes, the cluster is 6175 light-years away, spans 50 light-years across and has been estimated to be two million years old. Discovered by Herschel in 1785, the cluster lies approximately three degrees north of M27, the Dumbbell Nebula, and is high overhead around midnight during summer.

To the immediate northeast of NGC 6823 is a trunk-like pillar similar to those observed in other emission nebulae associated with stellar nurseries and star formation such as the Eagle Nebula (M16) in Serpens and the Lagoon Nebula (M8) in Sagittarius. As a result, protostars are also present in the immediate vicinity and include HH365 (north and just left of center) as well as HH165.

The small flaring reflection nebula near the bottom edge and to the right is NGC 6820 itself with a diameter of approximately 30 arc-seconds. NGC 6820 (or Sh2-86) was discovered by Albert Marth (1828-1897) in 1864. The nebulosity clearly visible in the image below is now typically regarded as NGC 6820.