A rare “black moon” will rise this weekend, marking a unique event in the lunar cycle. A new moon occurs when the moon passes between Earth and the sun, making its surface invisible from our planet. However, this particular new moon is special because it’s part of a rare phenomenon called a “seasonal black moon.”
A seasonal black moon occurs every 33 months, which is about to happen on Saturday. This event happens when there are four new moons in a single season, such as summer or winter. The third new moon in this sequence, which falls on August 23, is what’s known as a seasonal black moon.
The term “black moon” refers to the second new moon in a month, but it also has another meaning – it’s the opposite of a blue moon. A blue moon occurs when there are two full moons in a single month, and a black moon marks the start of the next full moon cycle.
This weekend’s seasonal black moon offers a great opportunity for stargazers to enjoy the summer stars on a moonless night. The Milky Way will be visible in the southeast, roughly from Vega, Deneb, and Altair. To see it at its best, find a location away from light pollution with no cities on the southern horizon.
The best way to view the Summer Triangle is to locate the three bright stars – Vega, Deneb, and Altair. The Milky Way will stream through the left side of the triangle, visible from Deneb down to Altair, then down to the southern horizon. This is a perfect night for stargazing, with minimal moonlight interference.
Source: https://www.livescience.com/space/the-moon/a-rare-black-moon-rises-this-weekend-what-is-it-and-what-can-you-see