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Normally, each season has three new moons, but the lunar cycle doesn't line up perfectly with our calendar. Every so often, an extra new moon sneaks in, and the third in that sequence is dubbed a black moon. The last seasonal black moon happened on May 19, 2023. Summer 2025 in the northern hemisphere is with a new moon on June 25th, followed by April 23rd, August 3rd, and September 21st. With four new moons squeezed into the season, the August 23rd new moon becomes the black moon. Seasonal black moons, like the ones on August 23rd, happen only about once every 33 months. There's also another definition of a black moon that refers to the second new moon in a single calendar month, which won't occur again until August 31st, 2027. Unlike a super moon or a lunar eclipse, a black moon isn't something you can watch unfold in real time. During the new moon phase, the moon is positioned between Earth and the sun, so its unlit side faces us, rendering it invisible against the sky. But don't be disappointed. The days immediately following the black moon will reveal one of the most beautiful lunar sights, the thinnest crescent. On the evenings of August 24th and August 25th, look toward the western horizon about 30 to 40 minutes after sunset to spot a delicate silver arc, the moon's first reappearance after going dark. The dark, moonless skies surrounding a new moon are also perfect for observing fainter deep sky objects that would otherwise be very difficult and sometimes impossible to see during brighter moon phases. It also makes for a particularly great time to study the dense core of the Milky Way.