M93, mag. +6.0, is a bright large open cluster of about 80 stars that's located in the southern constellation of Puppis. It has an apparent diameter of 22 arc minutes, corresponding to about 2/3rds that of the full Moon. Under dark skies, M93 is just about visible to the naked eye as a misty patch of light. It's an easy binocular object and a wonderful sight in small telescopes where the brightest stars are shaped like a triangle. The cluster was one of the last deep sky objects discovered by Charles Messier, which he catalogued on March 20, 1781.

Finding M93 is not difficult; it's positioned in western Puppis only a few degrees from the Canis Major border and not far from Sirius (α CMa) the brightest star in the night sky. Sirius shines at mag. -1.46 and can be easily found by connecting the three bright stars of Orion's belt and following the line southwards. Located 8 degrees southeast of Sirius are stars Omicron1 CMa (ο1 CMa - mag. +3.9) and Omicron2 CMa (ο2 CMa - mag. +3.0). Next imagine a line connecting these two stars and extend it eastwards, curving slightly southwards for about 10 degrees to arrive at M93.

M93 Open Cluster (David Malin/Australian Astronomical Obs.)

Finder Chart for M93 (also shown M41, M46 and M47)

Finder Chart for M93 (also shown M41, M46 and M47) - pdf format

A pair of 7x50 or 10x50 binoculars easily shows M93 and the triangular shape formed by the brightest stars. Through a small 80mm (3.1 inch) telescope at medium magnifications, M93 appears large and somewhat dense cluster. Towards the centre of the cluster is an arrowhead or wedge shaped grouping of bright stars. With averted vision, the nebulous background resolves into many fainter stars.

Larger telescopes of aperture 200mm (8-inch) or greater reveal dozens of members of mostly blue giants but some red giant stars that add to the charm of this already dazzling and beautiful cluster.

M93 has a spatial diameter of 20 light-years and is located 3600 light-years away. It's estimated to be about 100 million years old and is best seen from southern latitudes during the months of December, January and February.

M93 Data Table

Object TypeOpen Cluster
Distance (kly)3.6
Apparent Mag.6.0
RA (J2000)07h 44m 29s
DEC (J2000)-23d 51m 11s
Apparent Size (arc mins)22 x 22
Radius (light-years)10
Age (years)100M
Number of Stars80
Other NameCollinder 160

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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