When is the best time to observe Caldwell 98?

Caldwell 98 is best observed from February through April, with peak visibility during March when it transits around midnight in the Northern Hemisphere.

Where is Caldwell 98 located in the sky?

Caldwell 98 lies in the constellation Crux at right ascension 12h 42m and declination -62° 60′.

What telescope do I need to see Caldwell 98?

At magnitude 6.9, Caldwell 98 is easy in 7×50 or 10×50 binoculars.

Caldwell 98 — Open Cluster in Crux

NGC 4609

Open Cluster Excellent (68/100)

Magnitude 6.9^m OpenCluster Crux Visible

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

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About C98

Description

NGC 4609 is a small open cluster in Crux, about 4,200 light-years away. It contains about 40 stars within 5 arcminutes and lies just northwest of the Coalsack Nebula (C99), partially projected against the dark cloud.

Observing Tips

A compact, moderately rich cluster visible in a 4-inch telescope. Its proximity to the Coalsack Nebula creates a striking contrast between the bright cluster and the dark background. Best from southern latitudes in autumn and winter.

History

Discovered by James Dunlop in 1826 from Australia. Its position against the Coalsack makes it a popular target when observing the famous dark nebula.

Fun Facts

NGC 4609 appears to overlap with the Coalsack Nebula, but the cluster lies far beyond the dark cloud. The juxtaposition creates one of the finest examples of a bright cluster seen against a conspicuously dark background.

Observe

1Properties

Magnitude 6.9

Angular Size 5.4′

Distance 4,200 ly

Description

Open Cluster [Distance: 4200 ly]

Position & Identifiers

RA 12h 42m 17.8s

Dec -62° 59' 49.2"

Constellation Crux

Catalog C98

Also known as NGC 4609

Physical size

7.3 light-years across — about 1.7× 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 57 of 286 members.

3Visibility

Set a location in User Settings to see visibility data.

Best season Feb – Apr (peak: Mar)

4 Eyepiece View

Telescope Eyepiece

125x TFOV: 0.4° Lim. mag: 13.6

C98 · 5.4′ 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.