M50 is an appealing and relatively bright open cluster located in the rich star fields of Monoceros, close to the Canis Major border. With an apparent magnitude of +5.9, it's just about visible to the naked eye, appearing as a faint patch of nebulosity. Telescopically the cluster is moderately dense, contains a number of bright stars and spans about half the apparent diameter of the full Moon. It's a nice object for owners of small to medium size scopes.

The constellation Monoceros straddles the equatorial equator, east of majestic Orion and north of bright Canis Major. Despite lying in rich Milky Way star fields, Monoceros is a faint constellation with no stars brighter than 4th magnitude. Consequently, tracing the outline of this dim grouping requires some patience. However, it does contains a number of bright and interesting deep sky objects. In addition to M50, it's home to the Rosette Nebula (NGC 2237, 2238, 2239, and 2246), the Christmas Tree Cluster (NGC 2264) and Hubble's Variable Nebula (NGC 2261). All of these are best seen during the months of December, January and February

M50 was discovered by Charles Messier on April 5, 1772. However, it's possibly G.D. Cassini had already seen it before 1711, according to a report by his son in his book, "Elements of Astronomy".

M50 Open Cluster (credit:- NOAO/AURA/NSF)

Finder Chart for M50 (credit:- freestarcharts)

Finder Chart for M50 - pdf format (credit:- freestarcharts)

Finder Chart for M48 (also shown M50) (credit:- freestarcharts)

Finder Chart for M48 (also shown M50) - pdf format (credit:- freestarcharts)

Finding M50 is relatively easy. Start by aiming your sights on Sirius, the brightest star in the night-time sky. Located 9.5 degrees north-northeast of Sirius is M50, with θ CMa (mag. +4.1) sandwiched halfway between them. Through binoculars, M50 appears as a bright and relatively large patch of nebulosity with at least 2 or 3 stars resolvable. An 80mm (3.1-inch) scope shows a heart-shaped figure containing a sprinkling of mostly 7th and 8th magnitude blue-white stars, set against a background haze. Towards the southern edge of the cluster is a distinct orange star. The cluster is an attractive grouping when viewed at low to medium powers through 150mm (6-inch) or 200mm (8-inch) instruments. At least 40 mainly blue-white stars, but also the orange star and some yellow stars, are resolvable in this somewhat irregular shaped grouping. At about 100x magnification, the stars begin to overflow the eyepiece field of view with many fainter background members visible, bringing the total number to more than 80.

M50 covers 16 arc minutes of apparent sky. It lies at a distance of 3,200 light-years from Earth and has a spatial diameter of 20 light-years. In total, it contains over 100 stars and has an estimated age of 78 Million years.

M50 Data Table

Object TypeOpen cluster
Distance (light-years)3,200
Apparent Mag.+5.9
RA (J2000)07h 02m 42s
DEC (J2000)-08d 23m 26s
Apparent Size (arc mins)16 x 16
Radius (light-years)10
Age (years)78 Million
Number of Stars>100
Other NameCollinder 124

Sky Highlights - March 2017

Comet 41P/Tuttle-Giacobini-Kresak now visible with binoculars as it heads towards perihelion

Mercury heading towards greatest elongation east

Minor Planet
Vesta now visible with binoculars and small telescopes.

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for March 2017

Northern Hemisphere
West:- Venus (mag. -4.8 to -4.1 - first half of month), Mars (mag. +1.3 to +1.5), Uranus (mag. +5.9), Mercury (mag. -1.5 to -0.4 - second half of month)
Southeast:- Jupiter (mag. -2.3 to -2.5)
Southwest:- Jupiter
Southeast:- Saturn (mag. +0.5)

Southern Hemisphere
West:- Venus (first half of month), Mars, Uranus
North:- Jupiter
East:- Saturn
West:- Jupiter
Northeast:- Saturn
East:- Neptune (mag. +8.0 - second half of month)

Deep Sky
Naked eye / binoculars:-
Melotte 111 - Mel 111 - The Coma Star Cluster (Open Cluster)
Messier 44 - M44 - The Praesepe (Open Cluster)

Messier 67 - M67 - Open Cluster
Messier 51 - M51 - The Whirlpool Galaxy (Spiral Galaxy)
Messier 97 - M97 - The Owl Nebula (Planetary Nebula)
Messier 101 - M101 - The Pinwheel Galaxy (Spiral Galaxy)
Messier 65 – M65 – Spiral Galaxy
Messier 66 - M66 - Intermediate Spiral Galaxy
Messier 95 - M95 - Barred Spiral Galaxy
Messier 96 - M96 - Intermediate Spiral Galaxy
NGC 4244 - Spiral Galaxy
NGC 4565 - Needle Galaxy - Spiral Galaxy

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