For about four hours before every first quarter, sunlight catches three crater rims at the right angle and spells a letter X on the Moon.

The Lunar X sits on the terminator near the craters Blanchinus, La Caille and Purbach: the rims are already in sunlight while the ground around them is still dark, and the lit edges join up. There's a V nearby at the same time. Both are gone within a few hours as the Sun climbs. Binoculars will do it, but you have to be on time.