NGC 2477 is a stunning open cluster located in the Milky Way rich constellation of Puppis. It's arguably the constellations finest cluster which also contains other superb examples such as M46, M47 and M93. At magnitude +5.8, NGC 2477 is faintly visible to the naked eye but easily seen with binoculars and a fantastic telescope object, especially in medium to large scopes. It's listed as number 71 in the Caldwell catalogue.

The cluster was discovered by French astronomer Nicolas Louis de Lacaille during his tour of South Africa in 1751-52. In total it contains about 300 stars packed into an area 27 arc minutes in diameter with the brightest member star shining at magnitude +9.8. The four-magnitude difference between the combined cluster magnitude and the brightest component is an indication of how rich the cluster is.

NGC 2477 is too far south to have been included in Charles Messier's catalogue, but if he had observed from a more southerly latitude than Paris he almost certainly would have noticed this striking object. Twentieth century America astronomer Robert Burnham described NGC 2477 as "probably the finest of the galactic clusters in Puppis".

The cluster is easily found 2 degrees northwest of zeta Pup (ζ Pup - mag. +2.2) and just northwest of magnitude +4.5 star, b Pup. Located 1.5 degrees west of NGC 2477 and in the same binocular field of view lies large loose open cluster NGC 2451. Another binocular open cluster, NGC 2546, is positioned 4 degrees east of NGC 2477. They are best seen from southern latitudes during the months of December, January and February.

NGC 2477 - Open Cluster (ESO/J.Perez)

Finder Chart for NGC 2477

Finder Chart for NGC 2477 - pdf format

NGC 2477 can be glimpsed with the unaided eye as a hazy spot of light, but dark skies and good seeing conditions are essential. In 7x50 or 10x50 binoculars it appears as a beautifully large almost round fuzzy patch that hints on resolution. The cluster is a prominent object under dark skies but easily washed out with light pollution.

A small 80mm (3.1-inch) refractor at medium magnifications reveals a rich sparkling cluster with dozens of the brightest stars visible that looks somewhat like a very loose globular cluster. Since the member stars range from 10th to 14th magnitude, NGC 2477 is a spectacular sight in medium and large size scopes with many stars arranged in clumps and chains visible across the full cluster diameter. It's possible to fully resolve it right down to the core.

NGC 2477 is estimated to be at least 700 million years old. It's located 4,200 light-years distant and has an actual diameter of 32 light-years.

C71 Data Table

Object TypeOpen Cluster
Distance (ly)4,200
Apparent Mag.+5.8
RA (J2000)07h 52m 10s
DEC (J2000)-38h 31m 60s
Apparent Size (arc mins)27 x 27
Radius (light-years)16
Age (years)700 Million
Number of Stars300
Other Name (s)Collinder 165

Sky Highlights - September 2017

Neptune reaches opposition on September 5th

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for September

Northern Hemisphere
West:- Jupiter (mag. -1.7)
Southwest:- Saturn (mag. +0.5)
East:- Neptune (mag. +7.8)
South:- Neptune
East:- Uranus (mag. +5.7)
West:- Neptune
South:- Uranus
East:- Venus (mag. -3.9), Mars (mag. +1.8) (from second week), Mercury (mag. +0.5 to -1.3) (from second week)

Southern Hemisphere
West:- Jupiter
Northwest:- Saturn
East:- Neptune
West:- Saturn
North:- Neptune
Northeast:- Uranus
West:- Neptune
Northwest:- Uranus
Northeast:- Venus
East:- Mars (end of month)

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)

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