Caldwell 1 — Open Cluster in Cepheus
NGC 188
About C1
Description
NGC 188 is one of the oldest known open clusters in our galaxy, estimated at about 6.8 billion years old. Located in Cepheus near the north celestial pole, it lies roughly 5,400 light-years away and contains around 120 stars spread across 14 arcminutes.
Observing Tips
A challenging target requiring at least a 6-inch telescope to resolve individual stars. Located just 4 degrees from Polaris, it is circumpolar from most northern latitudes and can be observed year-round. Best seen at medium power (100-150x).
History
Discovered by John Herschel in 1831. Its extreme age makes it one of the most studied open clusters. Patrick Moore selected it as C1 for his Caldwell catalog, published in 1995 as a complement to the Messier catalog.
Fun Facts
At nearly 7 billion years old, NGC 188 is older than our Sun. Its survival is remarkable because most open clusters are torn apart by gravitational interactions within a billion years. The cluster orbits high above the galactic plane, which may explain how it avoided disruption.
Observe
1Properties
Position & Identifiers
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 |
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
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.
Each point is a Gaia-DR3 member. Colour encodes spectral type; size reflects membership probability.
Explore
8
Classification Decoder
Discover
9
Light Travel Time Machine
10
Relativistic Travel
Community Photos (1)
Credit: Kush.Chandaria. License: CC BY-SA 4.0. (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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