Horologium is a constellation of six stars faintly visible in the southern celestial hemisphere. It was first described by the French astronomer Nicolas-Louis de Lacaille in 1756 and visualized by him as a clock with a pendulum and a second hand. In 1922 the constellation was redefined by the International Astronomical Union (IAU) as a region of the celestial sphere containing Lacaille's stars, and has since been an IAU designated constellation. Horologium's associated region is wholly visible to observers south of 23°N.
Messier 73 is an asterism of four stars in the constellation Aquarius which was long thought to be a small open cluster. It lies several arcminutes east of globular cluster M72. According to Gaia EDR3, the stars are 1030±9, 1249±10, 2170±22, and 2290±24 light-years from the Sun, with the second being a binary star.
Messier 38 or M38, also known as NGC 1912 or Starfish Cluster, is an open cluster of stars in the constellation of Auriga. It was discovered by Giovanni Batista Hodierna before 1654 and independently found by Le Gentil in 1749. The open clusters M36 and M37, also discovered by Hodierna, are often grouped together with M38. Distance is about 1.066 kpc (3,480 ly) away from Earth. The open cluster NGC 1907 lies nearby on the sky, but the two are most likely just experiencing a fly-by, having originated in different parts of the galaxy.
Messier 67 and sometimes called the King Cobra Cluster or the Golden Eye Cluster is an open cluster in the southern, equatorial half of Cancer. It was discovered by Johann Gottfried Koehler in 1779. Estimates of its age range between 3.2 and 5 billion years. Distance estimates are likewise varied, but typically are 800–900 parsecs (2,600–2,900 ly). Estimates of 855, 840, and 815 pc were established via binary star modelling and infrared color-magnitude diagram fitting.
In astronomy, an open cluster remnant (OCR) is the final stage in the evolution of an open star cluster.
NGC 4609 is an open cluster of stars in the southern constellation of Crux. It was discovered on May 12, 1826 by the Scottish astronomer James Dunlop. The cluster has an apparent visual magnitude of 6.9 and spans an angular size of 6.5′. It is situated beyond the Coalsack Nebula at an estimated distance of 4,500 ly (1,379 pc) from the Sun.
NGC 654 is an open cluster in the constellation Cassiopeia. It was discovered by William Herschel in 1787. With apparent magnitude 6.5, it can be observed by binoculars. It is located 2,5° northeast of the star Delta Cassiopeiae. In the same low power field can also be seen the open clusters NGC 663 and NGC 659. It surrounds a 7th magnitude yellowish star, an F5Ia supergiant, which is a possible member of the group.
TW Horologii is a carbon star and semiregular variable in the southern constellation of Horologium, near the eastern constellation border with Reticulum. It has a ruddy hue and, with an apparent visual magnitude that ranges from 5.52 down to 5.95, is visible to the naked eye and one of the brightest carbon stars. Based on parallax measurements, it is located at a distance of approximately 1,370 light years from the Sun. It is drifting further away with a radial velocity of +14 km/s. In the past this star has been considered a member of the open cluster NGC 1252, but this now seems unlikely.
NGC 1901 is an open cluster in the Dorado Constellation. It has a bright middle and is a little rich, with stars from 7th magnitude downwards. The celestial object was discovered on 30 December 1836 by the British astronomer John Herschel. The cluster is sparsely populated with GAIA data suggesting a membership of around 80 stars. It is considered unlikely it will survive its next pass through the Milky Way’s galactic plane in about 18 million years time.
NGC 146 is a small open cluster in the constellation Cassiopeia. It was discovered by John Herschel in 1829 using his father's 18.7 inch reflecting telescope.
NGC 2539 is an open cluster in the constellation Puppis, located at the north edge of the constellation. It was discovered by William Herschel on January 31, 1785. It is a moderately rich cluster and with little central concentration, with Trumpler class II1m.
NGC 2659 is an open cluster in the constellation Vela. It was discovered by John Herschel on 3 February, 1835. It is of Trumpler class III3m. It is a young cluster, with age nearly 8 million years. The core of the cluster is 1.93 parsec across and the total radius is 3.6 pc. The total number of stars that belong to the cluster is estimated to be 1,801 ± 608 stars and the total mass 857 ± 237 M☉. Among its members, one is a Be star, with four more possible Be stars.
NGC 5662 is an open cluster in the constellation Centaurus. It was discovered by Nicolas Louis de Lacaille on May 17, 1752 from South Africa. James Dunlop observed it on July 10, 1826 from Parramatta, Australia and added it to his catalog as No. 342.
NGC 5617 is an open cluster in the constellation Centaurus. NGC 5617 forms a binary open cluster with Trumpler 22. It lies one degree west-northwest of Alpha Centauri.
NGC 5316 is an open cluster in the constellation Centaurus. It was discovered by James Dunlop in 1826. Located approximately 4,000 light years away from Earth, it is located in the Carina-Sagittarius arm.
NGC 2266 is an open cluster of stars in the constellation of Gemini. It was discovered by German-British astronomer William Herschel on 7 December 1785. This is a relatively dim cluster with an integrated visual magnitude of 9.5 and an angular size of 5.0′. The stellar members can be readily resolved with an amateur telescope. NGC 2266 is located at a distance of 10,603 ly (3,251.0 pc) from the Sun. It is located close to the opposite part of the sky from the Galactic Center, or the anti-center.
NGC 2527 is an open cluster in the constellation Puppis. It was discovered by William Herschel on December 9, 1784. The cluster was also observed by John Herschel on January 7, 1831. He also observed it on February 5, 1837, identifying it as a different object, which was catalogued as NGC 2520. It is a poor cluster and with no central concentration, with Trumpler class III1p.
NGC 7160 is an open cluster in the constellation Cepheus. It was discovered by William Herschel on November 9, 1789. The cluster was also observed by John Herschel on October 7, 1829. It is a poor cluster and with little central concentration, with Trumpler class II3p. It is part of the stellar association Cepheus OB2, located one degree south-southwest of VV Cephei.
NGC 6910 is an open cluster in the constellation Cygnus. It was discovered by William Herschel on October 17, 1786. The cluster was also observed by John Herschel on September 18, 1828. It is a poor cluster with prominent central concentration and Trumpler class I2p. NGC 6910 is the core cluster of the stellar association Cygnus OB9.
