Share An Evening With The First Quarter Moon

The moon strides between Sagittarius the Archer (a.k.a. the Teapot) and Capricornus the Sea Goat tonight. Source: Stellarium
The moon strides between Sagittarius the Archer (a.k.a. the Teapot) and Capricornus the Sea Goat tonight. Source: Stellarium

I’m a tireless moon booster. There are just so many ways of enjoying our only natural satellite. Whether walking by its light, trying to discern a rabbit, woman or man in that shiny ball or roving across its crater-riddled regolith (lunar soil) with binoculars and telescope, the moon is multi-dimensional.

Tonight it’s at half or first quarter phase, having completed a quarter of its orbit around the Earth. Half the moon is illuminated  by sunlight, the other half remains in nighttime shadow … but only for a short time. The terminator, the line separating day from night, creeps westward by degree; in seven days, the entire Earth-facing side of the moon will fill out and we’ll have a full moon.

Tonight's first quarter moon will show off several lunar "seas" or maria, a couple short mountain ranges and lots and lots of craters in the lunar highlands. Seven-power or higher binoculars will readily show craters. The terminator is the border between day and night on the moon. It moves to the left (lunar west) before full moon and to the right (east) after. Credit: Bob King
Tonight’s first quarter moon will show off several lunar “seas” or maria, portions of several mountain ranges and lots and lots of craters in the lunar highlands. Seven-power or higher binoculars will readily show craters. The terminator is the border between day and night on the moon. It moves to the left (lunar west) before full moon and to the right (east) after. Credit: Bob King

You’ll find the moon perched reasonably high in the southern sky around 7 o’clock local time this evening. Several dark lunar “seas” or maria (MAH-ree-uh) are visible with the naked eye. They’re ancient basins plowed out by asteroid impacts several billion years ago that later filled with dark, titanium-rich lavas. Long since solidified, they stare back at us as the dark spots we connect to make moon faces.

Drawing of the moon by Galileo. The Italian astronomer first observed the moon on November 30, 1609.
Drawing of the moon by Galileo. The Italian astronomer first observed the moon on November 30, 1609.

White terrain called the lunar highlands fills out much of the rest of the disk. Despite its creamy appearance, it’s rugged stuff — craters, crater rims, ejecta from craters and mountains. Not a soul knew it was there until Galileo and other early astronomers pointed the first telescopes moon-ward in the early 1600s.

One of the best moon’s tricks is the apparent brilliance of the lunar terrain. The Apollo astronauts who explored the moon were covered in charcoal-black moon dust. Of course, there are pale white rocks 240,000 miles up there, but much of the moon is dark and only appears bright because it’s set off by the much darker night sky.

During my moonlight walks, I sometimes talk out loud. It helps to clear my mind, work out an idea and connect me to the land. That’s another thing I like about the moon. Despite all my babbling, it’s never betrays a confidence.

Enjoy the evening.