When is the best time to observe Caldwell 82?

Caldwell 82 is best observed from April through June, with peak visibility during May when it transits around midnight in the Northern Hemisphere.

Where is Caldwell 82 located in the sky?

Caldwell 82 lies in the constellation Ara at right ascension 16h 41m and declination -48° 46′.

What telescope do I need to see Caldwell 82?

At magnitude 5.2, Caldwell 82 is visible to the naked eye from dark skies, easy in any binoculars.

Caldwell 82 — Open Cluster in Ara

NGC 6193

Open Cluster Showpiece (82/100)

Magnitude 5.2^m OpenCluster Ara Visible

Credit: Rbarba. License: CC BY 3.0. (Wikimedia Commons)

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About C82

Description

NGC 6193 is a bright open cluster in Ara, about 4,200 light-years away. It contains about 30 stars dominated by two brilliant hot O-type stars that illuminate the nearby Rim Nebula (NGC 6188). The cluster spans about 15 arcminutes.

Observing Tips

An easy and attractive target in binoculars and small telescopes. The two bright central stars are striking. The associated Rim Nebula (NGC 6188) requires an OIII filter and larger aperture. Best in summer from southern locations.

History

Discovered by James Dunlop on June 2, 1826 from Australia. The cluster is the energy source powering the photogenic Rim Nebula, a sculpted wall of dark molecular cloud being eroded by radiation.

Fun Facts

The two brightest stars in NGC 6193 are among the most luminous known, each pumping out hundreds of thousands of times the Sun's luminosity. Their UV radiation is sculpting the nearby molecular cloud into dramatic pillar structures visible in deep images.

Observe

1Properties

Magnitude 5.2

Angular Size 8.1′

Distance 4,300 ly

Description

Open Cluster [Distance: 4300 ly]

Position & Identifiers

RA 16h 41m 21.4s

Dec -48° 45' 43.2"

Constellation Ara

Catalog C82

Also known as NGC 6193

Physical size

9.7 light-years across — about 2.2× 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 71 of 417 members.

3Visibility

Set a location in User Settings to see visibility data.

Best season Apr – Jun (peak: May)

4 Eyepiece View

Telescope Eyepiece

125x TFOV: 0.4° Lim. mag: 13.6

C82 · 8.1′ 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.