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Directional Navigation Using the Moon

The moon has no light of its own. The light seen from the moon is a reflection of the sun.  The shape of the reflected light varies as the Earth orbits around the sun. This can be useful for finding direction at night once you understand how this works. When it is a crescent moon it is really easy.


moon navigation

To Find South during a Crescent Moon

  1. Imagine a line connecting the endpoints of the moon’s crescent and project it to the horizon.
  2. The point on the horizon indicates South. If you are in the Southern Hemisphere, such as New Zealand, this point indicates North.

To Find East-West

  • If the moon rises before the sun sets, the illuminated side is West.
  • If the moon rises after midnight, the illuminated side is East.

Although the example above is for the Northern Hemisphere (as the major portion of earth’s land is located here), it also works if you are in the Southern Hemisphere of the Tropic of Capricorn), such as New Zealand.

The reason this navigational method works is because the sun and move across the sky from east to west. Since the moon reflects the sun’s light, its bright side will be ‘pointing’ to the direction of the sun, or approximately east or west.

Moon Trivia (North Hemisphere)

When the moon moves away from the sun’s glare and out of the earth’s shadow, the moon reflects light from the right side and waxes to become a full moon. The right portion of the Moon is always growing (i.e., if the right side is dark, the Moon is growing darker; if the right side is lit, the Moon is growing lighter). After the full moon, it starts to wane, or lose shape and reflects light as a sliver on the left side.
  • The New Moon or No Moon always rises at sunrise.  It’s invisible because its illuminated side faces away from the Earth. Directional navigation won’t be possible because is too close to the sun’s glare to be visible.
  • The Crescent Moon follows the New Moon.  It will appear just after sunset in the western sky.
  • The Waxing Crescent Moon waxes to become a full moon. It reflects light from the right side as it moves away from the earth’s shadow.  The right 1-49% is visible.
  • The First quarter Moon rises at noon.  The right 50% is now visible. The illuminated side is West.
  • The Full Moon rises at sunset.  The full 100% of the moon is visible.
  • The Waning crescent moon wanes (loses shape) to become a new moon.  The left 1-49%  is visible.
  • The Last Quarter moon rises at midnight.  The left 50% is visible.
Image from Willem de pillem

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2 thoughts on “Directional Navigation Using the Moon”

  • Good stuff. I’ve printed this off and will take it into the mountains to see how it correlates with Southern Hemisphere data.

  • If one know the face of the Moon, he may use that to tell its direction. It rolls across the sky from east to west, clockwise if one be north of the Tropic of Capricorn, & anticlockwise of one be South of the Tropic of Cancer. Thus, one may see if it be in the ESE, or the ENE, or whatever. The rises with its east face, & sets with its west face. Ignore the telescope gazers’ directions, changed to suit them, in 1961.

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