New Moon The month of lunar phases starts with the New Moon But you cannot see the Moon at this time unless it gets in front of the Sun and causes a solar eclipse. Having just said that, why don’t we get a solar eclipse every month? The orbit of the Moon is tilted out of the ecliptic enough so that the Moon misses the Sun most of the time. There are only two times each year, when the Moon passes through a node of its orbit, when an eclipse is possible.

Waxing Crescent This is the phase of the Moon that most casual observers will see. It hangs low in the western sky at sunset, when people tend to be out and about in the early evening. This is the phase most often drawn in cartoons as well. Those drawings sometimes take advantage of a bit of artistic license, by the way. If drawn correctly for northern hemisphere observers, the Moon is illuminated from the right, and the middle of the bright edge, or limb, is always below the horizontal.

First Quarter It is called a first quarter because the Moon has moved one quarter of the way around in its monthly cycle. Many people might casually refer to this phase as a ‘half moon’. It sits high in the south at sunset and sets around midnight. Because of this, it is also the phase of the Moon seen by a majority of part-time sky watchers. During this phase of the Moon, the rugged highlands of the southern regions of the Moon stand out in sharp relief. My favorite trio of craters, Ptolemeus, Arzachel and Alphonsus are dramatically lit. Watch this cool video and enjoy these three craters to the sound of the blues.

Waxing Gibbous This is the ‘almost Full’ Moon. It is already above the horizon in the southeast as the Sun sets. A day or two before Full, it is illuminated enough so that a casual observer would interpret it as being Full. It spends most of the night above the horizon and sets just a few hours before sunrise.

Full What can we say about the Full Moon? It permeates all of our cultural heritages. Think about werewolves ! In this phase, the Moon opposes the Sun in every sense. It rises as the Sun sets, and sets when the Sun rises. When it is in that part of its orbit, there is always the chance that it will find Earth’s shadow. It is then that we might see a lunar eclipse. But we do not see an eclipse every Full Moon, of course. The tilt of the Moon’s orbit causes it to miss our shadow most of the time with lunar eclipses occurring once every six months or so.

Waning Gibbous It often happens that observers will see this phase in the west at dawn. This sometimes leads to confusion as those unfamiliar with the workings of the sky do not expect to see the Moon in the daytime sky. What is true is that, roughly speaking, the Moon is above the horizon for twelve hours every day. Which twelve hours of the day those are depends on the day of the month.

Third Quarter This phase of the Moon is not often observed owing to the fact that it rises at midnight and sets at noon. Casual observers might spot it in the south just before sunrise, but not many of us are skyatching at 5 AM! One notable thing about this phase is that it allows telescopic observers to see the Sun setting on the southern crater Tycho.