Messier CatalogueDemonstrate an awareness of, and use in a qualitative way, the Messier Catalogue
The French astronomer Charles Messier was a comet hunter. He was fed up of discovering objects that initially looked like comets but weren't, so he published a catalogue containing 110 of these objects.
These objects are of immense importance to astronomers as they are nebula and galaxies.
The objects are prefixed as 'M' so the Crab Nebula in Taurus is M1. He was restricted by the objects he could see from France, making list limited by today’s standards. It remains popular due to the length of time it has been around, as well as astronomers familiarity with the most common of these objects in it.
Other catalogues exist, notably the New General Catalogue.
In springtime some astronomers attempt Messier Marathons, during which they try to locate as many of these objects in one night as possible.