Messier 3 is a globular cluster in the constellation Canes Venatici. It was discovered by Charles Messier in 1764, and resolved into stars by William Herschel around 1784. This cluster is one of the largest and brightest, and is made up of around 500,000 stars.
It is located at a distance of about 33,900 light-years away from Earth. M3 has an apparent magnitude of 6.2, making it a difficult naked eye target even with dark conditions. With a moderate-sized telescope, the cluster is fully defined. It is estimated to be 8 billion years old. It is pretty difficult to spot this object in an amateur telescope without GoTo as it has no nearby pointer stars; though it is almost exactly halfway between and on a line connecting Cor Caroli with Arcturus.