A ‘True’ Blue Moon to Appear Aug. 22

A 'True' Blue Moon to Appear Aug. 22 a plane flies in front of a large moon in the dusk sky (Frank Rumpenhorst/AP)

By Nick Koutsobinas | Saturday, 21 August 2021 06:57 PM

A true blue moon will appear Aug. 22, bleeding into the dawn of Aug. 23.

But definitions, however, can be a tricky thing, according to Sky & Telescope magazine. By all accounts, the blue moon will be making its appearance in the original definition of the term rather than the Sky & Telescope version.

Drawing upon the definitions of a 1930s Farmer's Almanac, this type of "blue moon occurs when a season has four full moons, rather than the usual three." But such an event can only take place in the months of "November, May, February, or August, approximately one month before the Northern Hemisphere's winter and summer solstices and spring and autumn equinoxes."

Initially, we should expect to see a yellow-full, not blue, version of the moon if one decides to glint out the window at night.

One other type of the blue moon or the "Sky & Telescope' Blue Moon" version "occurs on the first or second night of a month having 30 or 31 days, respectively; there can never be this type of Blue Moon in February, because full moons occur 29.5 days apart."

Either way, both versions of a blue moon are rare, with both roughly occurring every 2.7 years.

The moon will reach peak illumination at around 8:00 a.m. ET on Sunday and will be visible into dusk.