When is the best time to observe Caldwell 106?

Caldwell 106 is best observed from August through October, with peak visibility during September when it transits around midnight in the Northern Hemisphere.

Where is Caldwell 106 located in the sky?

Caldwell 106 lies in the constellation Tucana at right ascension 00h 24m and declination -72° 05′.

What telescope do I need to see Caldwell 106?

At magnitude 4.0, Caldwell 106 is visible to the naked eye from dark skies, easy in any binoculars.

Caldwell 106 — Globular Cluster in Tucana

NGC 104

Globular Cluster Showpiece (96/100)

Magnitude 4.0^m GlobularCluster Tucana Visible

Credit: Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: J. Mack (STScI) and G. Piotto (University of Padova, Italy). License: CC BY 4.0. (Wikimedia Commons)

Star Map + List + Plan Star Hop

About 47 Tucanae

Description

47 Tucanae (NGC 104) is the second-brightest globular cluster in the sky (after Omega Centauri), located about 13,000 light-years away in Tucana. At magnitude 4.0, it is easily visible to the naked eye and spans 31 arcminutes, appearing projected near the Small Magellanic Cloud.

Observing Tips

One of the greatest deep-sky showpieces. Visible to the naked eye as a fuzzy star near the SMC. Binoculars show a large, bright, granular ball. Any telescope resolves it beautifully into thousands of stars. The dense, blazing core is unforgettable. Best from southern latitudes year-round.

History

First noted by Nicolas Louis de Lacaille in 1751. It has been observed by every major space telescope and is one of the most studied stellar systems in astronomy. It was designated "47 Tucanae" in Johann Bode's star catalog as if it were a star.

Fun Facts

47 Tucanae contains at least 25 millisecond pulsars, over 300 X-ray sources, and numerous blue stragglers. Despite a dense search, no planets have been found around its stars, suggesting that the crowded environment may prevent planet formation or survival.

Observe

1Properties

Magnitude 4.0

Angular Size 31.8′

Distance 13,400 ly

Description

Globular Cluster [Distance: 13400 ly]

Position & Identifiers

RA 00h 24m 05.8s

Dec -72° 04' 51.6"

Constellation Tucana

Catalog C106

Also known as NGC 104

Physical size

27 light-years across — tens of light-years across — wider than the solar neighbourhood

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

3Visibility

Set a location in User Settings to see visibility data.

Best season Aug – Oct (peak: Sep)

4 Eyepiece View

Telescope Eyepiece

30x TFOV: 1.7° Lim. mag: 13.6

47 Tucanae · 31.8′ diameter · N up, E left

5 Best Magnification

6Metallicity

[Fe/H] = -0.72 — these stars formed from gas about 5.2× poorer in iron than the Sun.

7Concentration class

Shapley-Sawyer class II — extremely centrally concentrated core.

Explore

8 Classification Decoder

Discover

Light Travel Time Machine

Relativistic Travel

Community Photos (1)

Credit: Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: J. Mack (STScI) and G. Piotto (University of Padova, Italy). License: CC BY 4.0. (Wikimedia Commons)

Skybred Mar 2, 2026