Caldwell 107 — Globular Cluster in Apus
NGC 6101
About C107
Description
NGC 6101 is a loose, sparse globular cluster in Apus, about 47,600 light-years away. It spans about 11 arcminutes and shines at magnitude 9.3, making it one of the fainter Caldwell globulars.
Observing Tips
A small, faint glow in a 6-inch telescope. An 8-inch scope begins to resolve a few outer stars. Its sparse nature means it never looks as impressive as the more concentrated globulars. Best from southern latitudes in winter.
History
Discovered by James Dunlop on June 1, 1826 from Australia. It is one of the least concentrated globular clusters known.
Fun Facts
NGC 6101 has one of the lowest central concentrations of any globular cluster. Studies suggest it may contain an intermediate-mass black hole that has gravitationally stirred the cluster, pushing stars outward and preventing core collapse.
Observe
1Properties
Position & Identifiers
2How easy to spot?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Easy | Medium+ | Medium |
| 150 mm Newton 150mm Newt. | Easy | Easy | Easy |
| Celestron C8 (203 mm SCT) C8 203mm | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
3Visibility
Set a location in User Settings to see visibility data.
4
Eyepiece View
5
Best Magnification
6Metallicity
[Fe/H] = -1.98 — these stars formed from gas about 95× poorer in iron than the Sun.
7Concentration class
Shapley-Sawyer class IX — diffuse profile with a loose outer envelope.
Explore
8
Classification Decoder
Discover
9
Light Travel Time Machine
10
Relativistic Travel
Community Photos (1)
Credit: NASA - Hubble Space Telescope. License: Public domain. (Wikimedia Commons)
Skybred Mar 2, 2026
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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