Crescent-spotting is a competitive sport. The youngest moon ever caught by naked eye was under sixteen hours old.

As the crescent thins, mountains along the limb break it into beads and then swallow it entirely, the Danjon limit, at roughly 7° from the Sun, below which no crescent is visible at all. Steven O'Meara logged one at 15 hours 32 minutes in 1990. The hunt happens at dusk, in the few minutes between the Sun setting and the Moon following it down.