The other day theAstronomy Picture Of The Day was about doing a Messier Marathon. Others have written much better than I can, so I’ll be brief.
Charles Messier cataloged 110 things in the sky in the 18th century. A Messier Marathon involves trying to see all 110 of them in the sky in one night. That’s pretty neato. I doubt I’ll ever do it, but it sounds like an adventure.
And now you know what a Messier Marathon is.