Don't forget to look up tomorrow night to witness a rare celestial phenomenon: the black moon.

The black moon (not to be confused with the blue moon) occurs when there are two new moons in one calendar month. Specifically, the side of the moon that's lit by the sun is facing away from Earth, which makes the moon completely invisible to us earth dwellers. Although the moon itself will be invisible to the naked eye, with no moonlight in the sky, a black moon makes for incredible stargazing. For Californians, the black moon—also known as the disappearance of the moon—will take place on September 30th at 5:11pm, but the effects of the black moon will last all night.

This rare sight happens only once every 32 months. The most recent occurrence was in March 2014, and after this week, the next black moon won't be until July 2019.

So don't forget to grab a blanket and lay out in your yard, on your rooftop, in a park, or on your terrace, and look up.

Want to make a night of it? Check out these six twinkling places to stargaze in the Bay Area.