Each month the moon passes through eight distinct phases, here’s your quick guide to understanding these moon shapes!
Moon phases, also called a lunar phase or phase of the moon, refers to the shape of the directly sunlit portion of the moon that we can see from Earth.
Moon shape basics
The moon takes approximately one month to orbit the earth, or exactly 29.53 days. The moon rises in the East and sets in the West each day. During this orbital cycle, based on the position of the moon between the earth and sun, portions of the moon become illuminated. Each of these appearances are called phases and have specific names.
The names of the 8 moon phases are: Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, Waning Crescent, New Moon.
The simple way to understand each lunar phase
To simplify the process of understanding moon cycles, we’ll start with the four intermediate phases which occur approximately each 7.4 days, where the moon is positioned along the ecliptic at 0°, 90°, 180°, and 270° respectively.
These four intermediate phases are: new moon, full moon, first quarter and last quarter. The other phases of the moon occur in between these four intermediate phases.
When the sun and moon are aligned on the same side of the earth, the moon is called “new.”
The term “waxing” moon refers to the amount of illumination on the surface of the moon increasing.
Just before the moon becomes full and just as is illumination starts to decrease again it is referred to as “gibbous.”
The term “waning” refers to the period of time after the moon becomes full and illumination begins to decrease again moving toward the new moon.
The 8 phases of the moon
One important thing to keep in mind: During the quarters, waxing or waning phases of the moon, whether you see the right side or the left side of the moon illuminated depends on whether you live in the northern or southern hemisphere. For example, at the first quarter, people living in the northern hemisphere will see the right side of the moon illuminated, while people living in the southern hemisphere will see the left side of the moon illuminated.
New moon: This is when the moon is blacked out from our viewpoint, and it appears that there is no moon visible in the sky. This occurs when the moon is positioned directly between the earth and the sun. In this phase, the entire far side of the moon is illuminated by the sun, but the side facing earth is completely shadowed.
Waxing Crescent: This occurs when between 1-49% of one side of the moon is illuminated.
First quarter: This is when 50 percent of one side of the moon is illuminated.
Waxing Gibbous: This occurs when between 51-99% of one side of the moon is illuminated.
Full moon: This is when the entirety of the moon is illuminated.
Waxing Gibbous: This occurs when between 99-51 % of one side of the moon is illuminated.
Last quarter: This is when 50 percent of one side of the moon is illuminated.
Waning Crescent: This occurs when between 49-1% of one side of the moon is illuminated.