M3

M3 is one of the brightest and largest globular clusters in the northern sky, located about 33,900 light-years from Earth in Canes Venatici. It contains roughly 500,000 stars in a sphere about 180 light-years in diameter. The cluster is renowned for its large population of variable stars — over 270 have been identified.

Located roughly halfway between Arcturus (Alpha Bootis) and Cor Caroli (Alpha Canum Venaticorum). Visible as a fuzzy star in binoculars. A 4-inch telescope at 100x shows a bright, round nebulous glow with a brilliant core. An 8-inch telescope resolves stars across much of the cluster, with beautiful chains radiating outward. Best observed from April through August.

Discovered by Charles Messier on May 3, 1764 — it was the first original discovery in Messier's catalog (M1 and M2 had been found by others). William Herschel resolved it into stars around 1784, counting an estimated 500 stars.