NGC 188 is an open cluster located in the far northern constellation of Cepheus. John Herschel, the son of William Hershel, discovered it on November 3, 1831. He originally recorded it as h34 in his 1833 catalogue and then as GC92 in his General Catalogue of 1864. The cluster eventually became NGC 188 in John L.E. Dreyer's New General Catalogue of 1888.

NGC 188 is positioned 4.75 degrees from the North Celestial Pole and is the northernmost open cluster in the sky. It's effectively circumpolar from all Northern Hemisphere locations. However, it can never be seen from latitudes south of 5 degrees south.

NGC 188 - Open Cluster (credit:- Roberto Mura)

Finder Chart for NGC 188 (credit:- freestarcharts)

Finder Chart for NGC 188 - pdf format (credit:- freestarcharts)

With an apparent magnitude of +8.1, NGC 188 is visible with binoculars. On dark nights, it can be spotted as a faint patch of light through 7x50 or 10x50 models. The cluster has a low surface brightness and is therefore best seen with medium size scopes or larger. A 150mm (6-inch) reflector reveals a soft glow of light that can initially appear unresolved, but on further inspection a sprinkling of faint stars can be made out. The brightest individual members shine at 12th magnitude and there are at least 130 stars above 17th magnitude. Through 250mm (10-inch) scopes, NGC 188 is a wonderful sight with dozens of stars visible across the entire cluster face. In total, it spans 15 arc minutes of apparent sky.

Studies indicate that NGC 188 is probably the oldest known open cluster and at least five billion years old. For comparison, the Pleiades (M45) cluster in Taurus is a youthful 115 million years of age. A factor contributing to the longevity of NGC 188 is it lies well away from the plane of the galaxy, and therefore has avoided disturbances that regularly occur in higher density star regions.

Since most open star clusters are young, they typically contain luminous hot blue giant stars. However, older clusters like NGC 188 tend to contain yellow and red stars and are almost devoid of blue stars.

NGC 188 has an actual diameter of 33 light-years and is estimated to be about 5,000 light-years away. It's the first object in the Caldwell catalogue.

NGC 188 Data Table

NGC188
Caldwell1
Object TypeOpen Cluster
ConstellationCepheus
Distance (light-years)5,000
Apparent Mag.+8.1
RA (J2000)00h 47m 30s
DEC (J2000)+85h 14m 29s
Apparent Size (arc mins)15 x 15
Radius (light-years)11
Age (years)5 Billion
Number of Stars>130
Other NameCollinder 6
Notable FeatureMost northerly open cluster in the sky

Sky Highlights - July 2017

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for July

Meteor Shower
Southern Delta Aquariids (Aquarids) meteor shower peaks on July 29

Northern Hemisphere
Evening
West:- Mercury (mag. -0.5 to +0.3) (second half of month)
Southwest:- Jupiter (mag. -2.0)
South:- Saturn (mag. +0.2)
Midnight
West:- Jupiter
South:- Saturn
East:- Neptune (mag. +7.8)
Morning
Southwest:- Saturn
South:- Neptune
Southeast:- Uranus (mag. +5.8)
East:- Venus (mag. -4.1)

Southern Hemisphere
Evening
West:- Mercury (second half of month)
Northwest:- Jupiter
East:- Saturn
Midnight
West:- Jupiter
North:- Saturn
East:- Neptune
Morning
West:- Saturn
North:- Neptune
Northeast:- Venus, Uranus

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

Shop at Amazon US

Contributions

If you like the website and want to contribute to the running costs then please do so below. All contributions are most welcome.

PayPal - The safer, easier way to pay online.