When is the best time to observe Caldwell 89?

Caldwell 89 is best observed from April through June, with peak visibility during May when it transits around midnight in the Northern Hemisphere.

Where is Caldwell 89 located in the sky?

Caldwell 89 lies in the constellation Norma at right ascension 16h 19m and declination -57° 56′.

What telescope do I need to see Caldwell 89?

At magnitude 5.4, Caldwell 89 is visible to the naked eye from dark skies, easy in any binoculars.

Caldwell 89 — Open Cluster in Norma

NGC 6087

Open Cluster Showpiece (78/100)

Magnitude 5.4^m OpenCluster Norma Visible

Credit: Roberto Mura. License: CC BY-SA 3.0. (Wikimedia Commons)

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About C89

Description

NGC 6087 is a bright open cluster in Norma, about 3,300 light-years away. It contains about 40 stars within 12 arcminutes, with the brightest member being the Cepheid variable star S Normae, which pulsates between magnitudes 6.1 and 6.8 over 9.75 days.

Observing Tips

A fine cluster for binoculars and small telescopes. The bright Cepheid S Normae stands out at the cluster's center. Monitoring its brightness changes over a week is a rewarding project. Best from southern locations in summer.

History

Discovered by Nicolas Louis de Lacaille in 1751 from South Africa. S Normae was discovered as a Cepheid variable by Roberts in 1895 and is one of the most accessible Cepheid variables for amateur observation.

Fun Facts

S Normae's membership in this cluster was crucial for calibrating the Cepheid period-luminosity relation, since the cluster's distance provides an independent distance measurement for the Cepheid — a key rung on the cosmic distance ladder.

Observe

1Properties

Magnitude 5.4

Angular Size 10.2′

Distance 2,900 ly

Description

Open Cluster [Distance: 2900 ly]

Position & Identifiers

RA 16h 18m 48.0s

Dec -57° 55' 58.8"

Constellation Norma

Catalog C89

Also known as NGC 6087

Physical size

9.2 light-years across — about 2.1× 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 84 of 226 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

C89 · 10.2′ 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.