Messier 103 (also known as M103, or NGC 581) is a small open cluster of many faint stars in Cassiopeia. It was discovered on 27 March 1781 by Pierre Méchain, but later added as Charles Messier’s last deep-sky object in his catalogue.
https://github.com/davepinch/pinchy.cc/blob/master/content/topics/astronomy/catalogs/messier/messier-103/en.wikipedia.org.md