Degree of difficulty 2 (of 5)

Minimum aperture Naked eye

Designation NGC 2682

Type Open cluster

Class II2r

Distance 2960 ly (K2005) 2890 ly (2004) 2960 ly (proper motion, 2002) 2450 ly (CMD, 1999)

Size 21 ly

Constellation Cancer

R.A. 8h 51.4min

Decl. +11° 49′

Magnitude 6.9

Surface brightness –

Apparent diameter 25′

Discoverer Köhler, 1779

History M 67 was discovered by Johann Gottfried Köhler in Dresden, Germany, before or in 1779. He described it as a “rather prominent nebula of longish shape,” but his observation was not published. Hence, Messier made an independent discovery of this cluster when he found it on the 6th of April 1780, and saw a “cluster of small stars with nebulosity.”

A few years later, William Herschel described M 67 as a “very beautiful and pretty much compressed cluster of stars, easily to be seen by any good telescope and in which I have observed above 200 stars at once in the field of view of my great reflector, with a power of 157.” His son John gave a brightness range of magnitude 11 to 15 for the cluster stars and wrote: “It is preceded by a rich region of stars of 9th and 10th magnitude.” D'Arrest saw a “dainty star cluster, the stars have a brightness of magnitudes 11 to 13,” while Smyth likened its shape to that of a “Phrygian cap,” like those worn by bishops.

Heinrich Maedler saw, like William Herschel, “about 200 stars in a space of 12' to 15' diameter. The stars differ a lot in their shimmer, and there is only little concentration toward the middle.” Leo Brenner commented: “In the viewfinder apparent as a nebulous patch, but already in low magnification recognizable as a star cluster and a splendid object. Surrounded by a semicircle of brighter stars, there are laid out 230 stars of magnitude 9 to 12.5.″ Finally, Curtis quoted a photographic diameter of 16'.