NGC 6281 is an open cluster

Open cluster

An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...

 of stars in the constellation Scorpius

Scorpius

Scorpius, sometimes known as Scorpio, is one of the constellations of the zodiac. Its name is Latin for scorpion, and its symbol is . It lies between Libra to the west and Sagittarius to the east...

. It was not included in the Messier

Messier object

The Messier objects are a set of astronomical objects first listed by French astronomer Charles Messier in 1771. The original motivation of the catalogue was that Messier was a comet hunter, and was frustrated by objects which resembled but were not comets...

 or Caldwell

Caldwell catalogue

The Caldwell Catalogue is an astronomical catalog of 109 bright star clusters, nebulae, and galaxies for observation by amateur astronomers. The list was compiled by Sir Patrick Caldwell-Moore, better known as Patrick Moore, as a complement to the Messier Catalogue.The Messier Catalogue is used...

 catalogues of nebulous objects, but it is the brightest such cluster in the constellation to be left out of both. It is readily observed with binoculars or a small telescope; it is located about to the east of Mu Scorpii

Mu Scorpii

The Bayer designation Mu Scorpii is shared by two star systems, in the constellation Scorpius:* μ¹ Scorpii* μ² ScorpiiThey are separated by 0.1° in the sky....

. James Dunlop

James Dunlop

James Dunlop was an astronomer's assistant who was hired by Sir Thomas Brisbane to work at his private observatory, once located at Paramatta , New South Wales, about twenty-three kilometres west of Sydney, Australia during the 1820s and 1830s...

 described the cluster as a "curiously curved line of pretty bright stars, with many stars mixt". John Herschel

John Herschel

Sir John Frederick William Herschel, 1st Baronet KH, FRS ,was an English mathematician, astronomer, chemist, and experimental photographer/inventor, who in some years also did valuable botanical work...

 then described the cluster as both "pretty bright" and "pretty rich".

This cluster has a tidal radius of 26 ly and a mass of about 214 solar mass

Solar mass

The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

es. It is classified as a type II2p cluster and has 55 members with a visual magnitude of 13.5 or greater within 20 arcminutes of the center. The brightest member is 9th magnitude. Overall, the cluster has an integrated visual magnitude of 5.4.