The Messier objects are a set of over 100 astronomical objects first listed by French astronomer Charles Messier in 1771. Messier was a comet hunter, and was frustrated by objects which resembled but were not comets, so he compiled a list of them, in collaboration with his assistant Pierre Méchain, to avoid wasting time on them. The number of objects in the catalog reached 103 during his lifetime but a few more thought to have been observed by Messier have been added by other astronomers over the years.