How To See August’s Rare Blue Moon Over Princeton

PRINCETON, NJ — Sky gazers, take note: This weekend brings more than a brief respite from the stresses of the workweek. It also brings a chance to catch a glimpse of a rare seasonal blue moon over Princeton.

The blue moon will adorn the night sky on Sunday. The last seasonal blue moon occurred on Halloween in 2020.

There are two instances in which we experience a “blue” moon. Many of us are familiar with the first instance: A blue moon happens when there are two full moons in a calendar month. The second is usually called a blue moon, according to The Farmers’ Almanac.

Turns out, that definition is more folklore than truth, The Farmers’ Almanac says.

The modern custom of naming the second full moon of any month a “blue moon” was actually based on a misinterpretation in an article written by James Hugh Pruett in the March 1946 issue of “Sky & Telescope” magazine. Titled “Once in a Blue Moon,” Pruett incorrectly summarized what he read in the Maine Farmers’ Almanac.

The second instance — the accurate definition of a blue moon and the type we’ll see Sunday — actually has to do with the number of full moons in a single season. Typically, there are 12 full moons each year, or three per season. If four full moons occur during a single season, the third is referred to as a “blue moon.”

Will you see this year’s blue moon over Princeton?

The National Weather Service predicts showers and thunderstorms Sunday night, preceded by mostly cloudy skies. Hopefully the rain will hold off just long enough to catch a glimpse of the moon!

If you miss this weekend’s blue moon, you’ll have a chance to catch the next one in just three short years.

The next seasonal blue moon will grace the skies on Aug. 19, 2024, followed by May 20, 2027.

So, is a blue moon actually blue? Not usually, according to EarthSky.org.

If you see a photo of a blue moon, chances are it was taken using a camera with a blue lens filter. On rare occasions, usually after vast forest fires or major volcanic eruptions, the moon has reportedly taken on a bluish or lavender hue, according to The Farmers’ Almanac. Soot and ash particles propelled into the Earth’s atmosphere can sometimes make the moon appear blue.

That being said, a full moon in any month or any season typically wouldn’t appear blue in color.

The blue moon is also a sure sign that autumn is on its way, according to EarthSky.org.

Since Sunday’s blue moon happens considerably closer to the fall equinox than the summer, the moon shares similar characteristics to September’s harvest moon. By definition, the harvest moon is the closest full moon to the autumn equinox. The true harvest moon will come on Sept. 20.