This month, the first quarter moon is found in front of the constellation Virgo and in between the planets Mars and Saturn. Ruddy Mars glowers very close to the Virgo star Zavijava, whereas golden Saturn shines fairly close to Virgo’s one and only first-magnitude star, sparkling blue-white Spica. Zavijava, though, is a faint fourth-magnitude star, so you may need binoculars to see it gleaming next to Mars.
The first quarter moon falls on June 27, 2012 at precisely 3:30 Universal Time (UT). Converting UT to the what the clock reads in our U.S. time zones, we find that the first quarter moon comes today – on June 26 – at 11:30 p.m. Eastern Daylight Time, 10:30 p.m. Central Daylight Time, 9:30 p.m. Mountain Daylight Time and 8:30 p.m. Pacific Daylight Time.
Photo credit: waiferx
For time zones in the mainland U.S., the moon will be above the horizon at that time, since a first quarter moon rises around noon, and sets around midnight. In other words, we in the U.S. will be seeing the moon tonight as it reaches the precise first quarter phase.
At quarter moon, half the lunar disk – the face of the moon we see from Earth – is illuminated by sunlight. Meanwhile, the other half of the moon’s face is engulfed in the moon’s own shadow. So why, people often ask, is the half-lit moon called a quarter moon?
We can offer some possible explanations. First of all, we can only see one-half of the moon’s globe. So if the half that we do see is half-lit, that means the lit portion represents only one quarter of the whole lunar globe. Remember learning in math class that 1/2 x 1/2 = 1/4?
Last Quarter Earth as seen from the first quarter moon (2012 June 26 at 10:30 p.m. CDT)
Secondly, the lunar month is said to begin at new moon. The moon completes one-fourth of its journey around the Earth at the first quarter phase. It completes three-quarters of its journey at the last quarter phase (which some people call a third quarter moon). Then the lunar month starts anew at new moon.
The first quarter moon waxes (increases) toward full moon, but the last quarter moon wanes (decreases) toward new. When we see a waxing first quarter moon from Earth, someone on the moon would actually see the Earth in its waning last quarter phase.
In a nutshell, a half-lit moon is called the quarter moon. See it tonight in front of the constellation Virgo, in between the planets Mars and Saturn.
Earth graphic courtesy of John Walker’s Earth And Moon Viewer
