Omicron Velorum Cluster (IC 2391)
History
The Omicron Velorum Cluster was first mentioned as «nebulous star» by Persian astronomer Al-Sufi in his «Book of Fixed Stars» from 964 AD. [364] French astronomer Nicolas-Louis de Lacaille first resolved it in 1751-1752 while observing it with his 1/2-inch refractor from the Cape of Good Hope. He described it as «a small cluster of stars» [730] Somehow John Herschel missed this cluster while observing from Cape of Good Hope in the years 1834 to 1838. Therefore it didn't receive a GC or NGC designation. Solon Bailey also found the cluster on a photographic plate in 1896 using a 1" (f/13) Cook lens at the Boyden station in Arequipa. He was credited for the discovery in Dreyer's «Second Index Catalogue» from 1910 [315] where this cluster was listed as IC 2391. [364]
John Herschel discovered NGC 2669 (h 3140) on 11 April 1834 and recorded «Cluster VIII class. A large, poor, loose cluster of stars, 10...13m.» The position was noted as very uncertain: RA 8h 40m ± and NPD 143° 21' ± in 1830 Epoch. At that position is nothing that matches his description. If one corrects the declination by +1° it matches the position of a small loose cluster. [364]
Physical Properties
| Name | RA | Dec | Type | vMag | Dim | MD | Dreyer Description | Identification, Remarks |
|---|---|---|---|---|---|---|---|---|
| NGC 2669 | 08 46 19.0 | -52 56 06 | OCL (II3p) | 6.1 | 14 | 1.046 | Cl, L, P, lC, st 10…13 | h 3140; GC 1701; OCL 768; ESO 165-SC5 |
| IC 2391 | 08 40 18.0 | -52 55 00 | OCL (II3p) | 2.6 | 60 | 0.176 | Cl, co, incl. ο Velorum 3.7 mag | OCL 767; ESO 165-SC4; Omikron Vel cluster |
Finder Chart
The open cluster cluster IC 2391 is located in the constellation Vela. Unfortunately it is not visible from Europe. On 29 January it in opposition with the Sun and is therefore highest in the sky at local midnight.
