Tonight’s Full Moon For Maple Syrup Lovers

A fine 22-degree halo rings the nearly full moon last night as seen from Duluth, Minn. Jupiter (lower left) managed to avoid getting snared. Halos form when light is refracted or bent through tiny, pencil-shaped ice crystals in high cirrus or cirrostratus clouds. Credit: Bob King

My first photo ever published in a daily newspaper showed my landlord tapping the big maple tree outside his home. I’m guessing the month was March, the traditional time for lovers of maple syrup to drill a hole in a tree, tap in the spile and hang a bucket to collect the sap. Native peoples call it the sugarbush season and boiling the sap down into sweet syrup has been an important part of American culture since before there was an America. It’s no surprise that certain tribes named the March full moon the Full Sap Moon.

The moon rises tonight near the juncture of two important imaginary circles in the sky: the ecliptic, the path followed by the sun, moon and planets across the sky, and the celestial equator. The celestial version is just the Earth’s equator projected onto the sky. It always intersects the horizon at the due east and due west points. Since the moon’s path (ecliptic) takes it near the equator at full moon around the time of the equinoxes, tonight’s full moon will rise nearly straight east. Created with Stellarium

It has other names, too including Full Crust Moon, for the hardened snow crust that forms after repeated thawing and refreezing, and Full Worm Moon, recalling the return of the earthworms. While it’s a little too early for that here in northern Minnesota, it’s never too early to enjoy the full moon rising. Use this moonrise calculator to find out when the moon comes up for your town, and if it’s clear tonight, set aside a half hour to contemplate the orange orb. The moon will rise almost due east in the constellation Virgo around sunset and remain visible the entire night.

It’s always a good idea to look up when the clouds are high and thin as they were this morning, when we were treated to a uncommon 46-degree halo (faint outer circle near the top), a bright 22-degree halo and a shapely Parry Arc atop the smaller halo around the sun. There’s even a hint of a parhelic arc cutting across the halo to the left and right of the sun. All the phenomena are caused by light refracted in different ways through pencil-shaped crystals. Credit: Bob King

I like to bring a pair of binoculars with me for moonrises to better appreciate the interesting atmospheric effects that can ripple and shimmer the moon’s outline, squeeze it into an oval and color its edges purple and green. Our sightline to the moon passes through the lowest, densest part of the air column across hundreds of horizontal miles. Changes in air temperatures and jumbled up winds across such a large distance greatly affect the moon’s appearance. Refraction, the bending of light to different degrees according to the density or “thickness” of the air is responsible for the moon’s out-of-round shape.

Sugar-making among the Indians of the North from the Library and Archives of Canada. Credit: William De La Montagne, 1840-1922

The bottom of the atmosphere also contains the most dust, salt and industrial pollutants which scatter away the cooler blues and greens from moonlight, giving it a mellow, pink-orange glow. Watch for these things tonight while relaxing at tonight’s rising of the Sap Moon.

4 Responses

  1. The tapping of the Maple trees and the hanging buckets also bring the 1st flies out, attracted by the sweet sap only to drown at the bottom. Helping my uncle collecting the sap as a pre-teen, I was always surprised to see them even with lots of snow left on the ground.

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