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Understanding the 8 Phases of the Moon

Like the Earth, the Moon is always half illuminated by the Sun. The Moon always has a day side and a night side. From the Earth vantage point we see varying fractions of its day and night sides. Here are the eight phases of the Moon and what they look like...

Paul Bodnar      Educational     6/29/2021
Paul Bodnar
Educational
6/29/2021

Top 3 Keys to Understanding Moon Phases

1. When you see the Moon, try to picture where the Sun is.

It is important to remember that the Sun is illuminating the Moon and creating 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

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

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 Moon Phase

Last Quarter

About 21 days from the New Moon you observe the left half of the Moon.


Waning Crescent

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

Understanding the Moon phases can get confusing.  If you forget which way the Moon phases go, just 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.

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A lake reflects a nearby wildflower meadow and trees.
Showers Lake Vista, Tahoe Rim Trail
Photo courtesy of the Tahoe Rim Trail Association

Trail guides that get you to places you’ve dreamed of.

As the makers of Guthook Guides, Bikepacking Guides, and Cyclewayz, we help you navigate the most popular trails around the world on your smartphone. Our hiking guides and biking guides work completely offline. Let Guthook guide your next adventure!

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About the Author
A man wearing an Arizona Trail baseball cap stands in a field in front of a mountain.

Paul Bodnar

Paul has always liked hiking and thru-hiked the Pacific Crest Trail in 1997 after college. After years of working in chemistry, he wanted to create a career involving the outdoors, so he hiked the PCT again in 2010 to do research for his guide book, Pocket PCT. He realized that creating a smartphone app for navigating the outdoors would make it easier to keep the data current and provide a better way to navigate. While hiking with Ryan (aka Guthook) in 2010, they decided to work together to create the first comprehensive smartphone guide for the PCT.