Courtesy of EarthSky
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The first quarter moon falls today at 6:42 p.m. Central Time. (That’s 7:42 p.m. Eastern time, 5:42 p.m. Mountain Time and 4:42 p.m. Pacific Time.) At first quarter phase, the lunar disk is half-illuminated in sunshine and half-engulfed in the moon’s own shadow. In other words, you are seeing half of the moon’s daytime side and half of the moon’s nighttime side.
The moon is in front of the constellation Taurus the Bull this evening, shining in between the Pleiades star cluster and the Bull’s brightest star, Aldebaran. The Pleiades cluster is also called the Seven Sisters, even though most people can only see six Pleiades stars with the unaided eye. If the moonlit glare makes it difficult to see the Pleiades’ dipper-shape pattern of stars tonight, try using binoculars.
The shadow line running across the lunar disk is called the terminator. It is along the terminator that you have your best views of the lunar landscape with binoculars or a telescope. The intermingling of light and shadow along the terminator line gives a wonderful three-dimensional portrayal of the lunar mountains, craters and valleys.
When the moon is waxing (increasing) from new to full, the terminator shows you where it’s sunrise on the moon.
Written by Bruce McClure
Other Links:
The York County Astronomical Society
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