IC 4756

IC 4756
Observation data (J2000 epoch)
Right ascension18h 38m 31.2s[1]
Declination+05° 29′ 24″[1]
Distance1.3 kly (400 pc)
Apparent magnitude (V)4.6[1]
Physical characteristics
Other designationsCr 386, Mel 210
Associations
ConstellationSerpens
See also: Open cluster, List of open clusters

IC 4756 is a large bright open cluster in the constellation Serpens. Known as Graff's Cluster, it is bright enough to be seen with the naked eye and considered a fine cluster for binoculars or small telescopes.[2]

IC 4756 is also known as the Tweedledee Cluster (paired with NGC 6633 as Tweedledum), also as the Secret Garden Cluster.[3]

Metallicity of IC 4756 is similar to the Sun, at -0.02±0.01 dex.[4]

Open star clusters IC 4756 (left) and NGC 6633. Original astrophoto.
  1. ^ a b c "IC 4756". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 30 November 2016.
  2. ^ Michael Bakich. "The Omega Nebula, Graff's Cluster, and planetary nebula IC 1295". astronomy.com. Retrieved 2020-10-05.
  3. ^ O'Meara, Stephen James (2007). Deep-Sky Companions: Hidden Treasures. Cambridge University Press. p. 457-458. ISBN 978-0521-83704-0.
  4. ^ Bagdonas, Vilius; Drazdauskas, Arnas; Tautvaišienė, Gražina; Smiljanic, Rodolfo; Chorniy, Yuriy (2018), "Chemical composition of giant stars in the open cluster IC 4756", Astronomy & Astrophysics, 615: A165, arXiv:1804.01975, Bibcode:2018A&A...615A.165B, doi:10.1051/0004-6361/201832695, S2CID 118857628