Tonight's moon out of the blue

Once in a blue moon, we actually get one. Does tonight's qualify? That depends on your astronomical, and linguistic, viewpoint.

Because the Western calendar is misaligned with the heavens, it's out of sync with moon phases. So tonight - technically tomorrow at 3:43 a.m. - Northwest stargazers may see July's second full moon, popularly called a blue moon.

Two moons in one month are not rare, but they are unusual, gracing us every couple of years - once in a blue moon. The next occurs Jan. 31, 2018. Visibility should be good, if incomplete, by late evening, although the orb will be less blue than belewe.

In Old English "belewe" meant betray - a betrayal of the moon's usual monthly appearance, sometimes interfering with church Lenten schedules of yore, hence a belewe moon. Mispronounce that over time and you'll get blue, as the story goes.

But to astronomers this belewe moon might be considered a fake. A poseur. A mistake. At minimum, call the second moon in one month Blue Moon Definition 2.

Originally, a belewe moon meant the third full moon in an astronomical season which contains four. Back up a sec; an astronomical season has three months, i.e. three full moons. So when a season contains four moons (every three to four years, but on different dates than Definition 2), the third moon in that season is the belewe, or blue, moon. July 2015 has no blue moon under this definition; the next is in May 2016.

So how did Definition 2 come about? A 1946 magazine article which (mis)interpreted astronomical data in a Farmer's Almanac, calling a month's second full moon a blue moon. Yup; blame the writer.

Anyway, rarely does a moon actually appear blue. That's an obscuration effect of dust or smoke particles of a certain size, about 0.7 microns, such as after dust storms or volcanic eruptions. Forest fires paint the moon too, sometimes tinting it pink or orange.

Whatever its color, tonight's moon comes right out of the blue.

Sholeh Patrick is a columnist for the Hagadone News Network. Contact her at Sholeh@cdapress.com.