OMICRON VELORUM CLUSTER AKA IC 2391

OPEN CLUSTER IN VELA (THE SHIP SAIL)

(ra: 08h 40'/ dec -52º 55')

March 2026, Home Backyard in Martinez, Buenos Aires, Argentina

DATA

TYPE: Open Cluster

Visual Brightness: 2.6

APPARENT DIAMETER: 60 arc minutes

DISTANCE: 490 light years

IMAGE INFORMATION

SCOPE: AKSAR 180 FMA  

CAMERA: QSI 583 WS

MOUNT: SKYWATCHER EQ3, OAG with QHY 5II Mono

FILTERS:  OPTOLONG LRGB Set HA ASTRONOMIK 7NM

SKY CONDITIONS: Urban Skies. Bortle 9

EXPOSURES: LHARGB (45,60,45,45,45) - all channels bin 1x1

OBJECT DESCRIPTION AND IMAGE SESSION

IC 2391 (also known as the Omicron Velorum Cluster or Caldwell 85) is an open cluster in the constellation Vela consisting of hot, young, blueish stars, some of which are binaries and one of which is a quadruple. Persian astronomer A. a.-R. al-Sufi first described it as "a nebulous star" in c. 964. It was re-found by Abbe Lacaille and cataloged as Lac II 5. IC 2391 contains about 30 stars with a total visual magnitude of 2.6, spread out across 60 arc minutes.

The background nebulosity in the image is coming from Gum 12 a vast and dim nebulosity. Gum 12 is an emission nebula that extends across 36° in the southern constellations Vela and Puppis. It lies approximately 450 parsecs from the Earth so it is far away from the cluster. Hard to distinguish without dedicated filters, it was widely believed to be the greatly expanded (and still expanding) remains of a supernova that took place about a million years ago. More recent research suggests it may be an evolved H II region. It contains the 11,000-year-old Vela Supernova Remnant, along with the Vela Pulsar.

Above IC 2391 we have NGC 2669 which is an open cluster of 14 arc minutes in size and shines at magnitude 6.1 and a distance between 2100 and 3400 light years from earth.