When is the best time to observe Caldwell 85?

Caldwell 85 is best observed from December through February, with peak visibility during January when it transits around midnight in the Northern Hemisphere.

Where is Caldwell 85 located in the sky?

Caldwell 85 lies in the constellation Vela at right ascension 08h 40m and declination -53° 04′.

What telescope do I need to see Caldwell 85?

At magnitude 2.5, Caldwell 85 is visible to the naked eye under most conditions.

Caldwell 85 — Open Cluster in Vela

IC 2391

Open Cluster Showpiece (95/100)

Magnitude 2.5^m OpenCluster Vela Visible

Credit: YayLol123. License: CC BY-SA 4.0. (Wikimedia Commons)

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About Omicron Velorum Cluster

Description

The Omicron Velorum Cluster (IC 2391) is a bright, nearby open cluster in Vela, about 574 light-years away. At magnitude 2.5, it is easily visible to the naked eye and contains about 30 stars spanning 50 arcminutes, centered on the bright star Omicron Velorum.

Observing Tips

A fine naked-eye and binocular cluster. Too spread out for most telescopes — binoculars at 7-10x give the best view. The cluster is dominated by Omicron Velorum (mag 3.6). Best from southern latitudes in late winter and spring.

History

Known since antiquity as a naked-eye grouping. First cataloged by Nicolas Louis de Lacaille in 1751. It was one of the clusters used to determine the age of nearby stellar associations.

Fun Facts

At only 50 million years old, IC 2391 is a young cluster whose stars are still settling down. Several of its stars show strong X-ray emission characteristic of magnetically active young stars.

Observe

1Properties

Magnitude 2.5

Angular Size 29.1′

Distance 574 ly

Description

Open Cluster [Distance: 574 ly]

Position & Identifiers

RA 08h 40m 16.6s

Dec -53° 03' 32.4"

Constellation Vela

Catalog C85

Also known as IC 2391

Physical size

4.1 light-years across — about 0.9× the Sun-to-Alpha-Centauri distance

2How easy to spot?

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
150 mm Newton 150mm Newt.	Easy	Easy	Easy
Celestron C8 (203 mm SCT) C8 203mm	Easy	Easy	Easy

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

Easy on Seestar S50

At 150mm under B5 skies you should resolve about 63 of 222 members.

3Visibility

Set a location in User Settings to see visibility data.

Best season Dec – Feb (peak: Jan)

4 Eyepiece View

Telescope Eyepiece

50x TFOV: 1.0° Lim. mag: 13.6

Omicron Velorum Cluster · 29.1′ diameter

5 Best Magnification

6Where this cluster sits in time

Open clusters span more than four orders of magnitude in age — from newborn OB associations to ancient, metal-rich survivors.

7 Colour-Magnitude Diagram

A cluster's colour-magnitude diagram reveals its age: the bluer the turn-off point where the main sequence bends into red giants, the younger the cluster.

Loading member data…

Each point is a Gaia-DR3 member. Colour encodes spectral type; size reflects membership probability.