Messier Marathon
Here is a
plot showing the locations of Messier objects in the sky.
Declination and
right ascension are the celestial equivalent of
latitude and
longitude. This doesn't show the whole sky. Messier included only objects that were visible from Paris, his observing location, around 49 degrees N. But, of course, most are visible from a wide range of latitudes, including the southern hemisphere.
A Messier marathon involves trying to locate as many of the Messier objects as possible in one night. You can well imagine that this is a demanding test of sky knowledge and stamina. Such events are often organized by astronomy clubs.
Sounds pretty strenuous to me - is there such a word as mastrochist, I wonder.