This phase is named as such because it starts a new lunar cycle. At this time, the Sun and Moon are in conjunction, meaning that they are closest together in the sky, on the same side of Earth (Sun→Moon→Earth). From our perspective, the Moon appears totally dark: We can not usually see it because we are facing the Moon’s shadowed side, which does not receive any direct sunlight. But if we were to travel to the other side of the Moon, the part that faces the Sun, it would be totally illuminated.

This phase occurs between the new Moon and first quarter phases. At the beginning of this stage, we see a thin, crescent-shape Moon, which, in the Northern Hemisphere, appears on the right side. The lit area slowly widens each day, covering more and more of the right side of the Moon’s surface until the first quarter phase, when the Moon’s entire right side is illuminated. (In the Southern Hemisphere, the same thing happens, only on the left side.)

This phase got its name because at this point the Moon has traveled 1/4 of the way through its orbit. It’s a confusing label, though, because at this time from our perspective, 1/2 of the Moon’s surface is lit. In fact, both the first and last quarter phases are sometimes called a Half Moon. At first quarter in the Northern Hemisphere, the right side of the Moon is illuminated; in the Southern Hemisphere, it’s the left side. In actuality, we are seeing 1/2 of the lit side of the Moon because the entire illuminated surface is only partly facing our direction. In other words, the Moon is perpendicular to the Earth/Sun line. During a first quarter phase, the Moon is said to be at east quadrature, meaning that it is 90 degrees east of the Sun when viewed from Earth.

This phase occurs between the first quarter and full Moon and describes the Moon when it is more than half lit, but not yet fully. At the beginning of this stage in the Northern Hemisphere, we see the right half of the Moon illuminated plus a tiny fraction more extending into the left side. As the days pass, the light creeps farther left, covering more and more of the Moon surface until the full Moon phase, when the entire disk is illuminated. In the Southern Hemisphere, the same happens, only from left to right. Gibbous comes from a Latin word meaning “humpbacked,” referring to the curved lit area on the Moon surface.

This phase is named as such because, from our perspective, the full disk is illuminated. At this time, the Sun and Moon are in opposition, meaning that they are farthest apart in the sky, on opposite sides of Earth (Sun→Earth→Moon). Occasionally, if the full Moon’s position lines up correctly with the Sun and Earth, from our viewpoint, the Moon will enter Earths shadow, which will cut off part or all of the sunlight reflected off the Moon surface, thereby causing a lunar eclipse.

This phase occurs between the full and last quarter and describes the Moon when it is more than half lit, but not fully. At the beginning of this stage in the Northern Hemisphere, we see a disk almost fully lit except for a tiny sliver on the right side that is in darkness. As the days pass, the lit area shrinks from right to left until the last quarter phase, when the Moon’s left half is illuminated and the right half is in darkness. In the Southern Hemisphere, the same happens, only the light shrinks from left to right.

This phase got its name because at this point the Moon has traveled 3/4 of the way through its orbit, and has just one more (the last) quarter to complete one revolution. This stage is sometimes also called Third Quarter. At this stage, we see 1/2 of the Moon’s surface lit. In the Northern Hemisphere, the left side is illuminated; in the Southern Hemisphere, it is the right side. During a last quarter phase, the Moon is said to be at west quadrature, meaning that it is 90 degrees west of the Sun when viewed from Earth.

This phase occurs between the last quarter and new Moon phases. At the beginning of this stage, in the Northern Hemisphere, we see the Moon’s entire left side almost fully lit and the right side in darkness. The lit area slowly shrinks each day, covering less and less of the Moon’s surface until it looks like a very thin crescent on the left side. Eventually, the entire disk will be in darkness, at which point it will be the new Moon phase and another lunar cycle will have begun. (In the Southern Hemisphere, the same thing happens, only the lit area would have started on the right side and shrunk from left to right, until a thin crescent remained on the right.) Once the Sun rises, it is not easy to see this slim phase; the best time is before the glare of sunrise.