Once in a Blue Moon

Lunar eclipse by Randy Brewer

December 30, 1982: The only total lunar eclipse of a Blue Moon in the last century occurs. A “blue moon” is not about color, but about the rarity of the event. It is the second full moon in a calendar month. There were 41 Blue Moons in the 20^th century. There were four eclipses during Blue Moons in the same 100 year period, but this date produced the only Total Eclipse of a Blue Moon.

The lunar cycle, or the time it takes for the moon to travel through its phases, is 29 days, 12 hours, and 44 minutes. The phases of the moon are based on what we can see in the night sky. The Moon is non-luminous, only reflecting sunlight, not producing light on its own. What we see, whether a New Moon [no Moon at night], a crescent shape, or even a Full Moon, is created by the triangulation of the Sun, Moon, and Earth.

The Moon is always half lit, but we can only see portions of it because of the relation of the three bodies. A New Moon means that the half that is lit by the Sun faces away from Earth. A Full Moon means just the opposite, the Sun is behind the Earth and fully illuminating the face toward us. The orbit of the Moon is 5º tilted from the orbit of the Earth around the Sun. If this were not so, there would always be eclipses.

An eclipse occurs when the shadow of the Earth [Latin term – umbra] passes over the illuminated face of the Moon. The bodies line up 2-4 times each year. About 35% of the time there is a penumbral [Latin term – almost shadow] eclipse that is difficult to see even with a telescope. Another 30% of eclipses are partial while the last 35% are total eclipses. The first lunar eclipse was recorded in 721 BC by Ptolemy in Almagest. Lunar eclipses, unlike solar eclipses, can be seen anywhere on Earth during the nights they occur.

“It’s only during an eclipse that the Man in the Moon has a place in the sun.” – unknown

“When a finger points to the moon, the imbecile looks at the finger.” – Chinese proverb

“The moon is nothing / But a circumambulating aphrodisiac / Divinely subsidized to provoke the world into a rising birth-rate.” – Christopher Fry

“I don’t know if there are men on the moon, but if there are they must be using the earth as their lunatic asylum.” – George Bernard Shaw

Also on this day, in 1610 the Blood Countess was finally stopped.