Top 3 Keys to Understanding Moon Phases
1. When you see the Moon, try to picture where the Sun is.
To better understand the phases of the moon it is important to remember that the Sun is illuminating the Moon. This creates the dayside of the Moon you observe. The Moon phases depend on where the Moon is positioned in relation to the Sun and the Earth.
2. The Moon rises in the east and sets in the west each day.
The Earth’s continuous spin causes causes the Moon to rise in the east and set in the west. So when you see the Moon in the west after sunset you know it is a setting moon not a rising Moon.
3. The Moon takes about a month to orbit the Earth.
The Moon moves about 12 to 13 degrees a day while orbiting the Earth or 360 degrees each 27.3 days. This is a slower and less noticeable motion of the Moon.
There are 8 phases of the Moon to track each month
New Moon
During the New Moon the side of the Moon facing the Earth is not illuminated by the Sun. The Moon surface facing Earth is dark because the Moon is between Sun and Earth.
Waxing Crescent
As the Moon grows (waxes) into its crescent phase look for a silvery looking crescent. A little part of the right side of the Moon is lit.
First Quarter
About 7 days after the New Moon the Moon is in the first quarter. Only half of the right side of the Moon is visible.
Waxing Gibbous
After the first quarter, most of the right side of the Moon is visible.
Full Moon
About 14 days after the new New Moon the Sun lights up the entire surface of the Moon.
Waning Gibbous
The appearance of the Full Moon diminishes and starts to get smaller or wane. About 3/4 of the left side of the Moon is lit.
Last Quarter
About 21 days from the New Moon you observe the left half of the Moon.
Waning Crescent
The Waning Crescent is the last phase of the Moon before returning to New Moon. At this phase you can only see a small sliver of the Moon on the left side.
Summary
Remembering the Moon phases can get confusing. If you forget which way the Moon phases go, remember “white on right, getting bright”. If the right side of the Moon is illuminated then the Moon is transitioning to a fully illuminated Full Moon.
For navigation using the night sky you might find learning about the North Star interesting.