Sailboat Under the Stars

How to Use the Stars for Navigation

These days, it might seem inconceivable that anybody could get lost, what with a GPS device on every smart phone and almost universal cell phone coverage. However, cell phone batteries have the nasty habit of dying unexpectedly, so if ever you need to find your way home by navigating with the stars, here is how to do it by observing the night sky, provided that the stars are visible of course.

Find North with Polaris

You may not always know where the North Star is, but if you can see the Plough, (Big Dipper) asterism in Ursa Major, you can easily find the star. The star is called the North or Polar star because it is located almost on the celestial North Pole, which coincides with the earth’s North Pole. So, how to find it?

If you can see the Plough, all you do is simply draw a line from the two stars that form the upright of the “cup” opposite the “handle” to a bright star that is about 5 times the distance between the two stars away, as per the drawing below. Once you have located the Pole star, you will notice that it is also the last star in the tail of the Little Bear, Ursa Minor. There is no chance of mistaking the Pole star for anything else; it is the brightest star in that spot.

Image credit:
Image credit:

It does not matter where in the northern hemisphere you are; once you have located the Pole Star you only need to draw a vertical line down from it toward the horizon. This point on the horizon may not be exactly due north, but it is close enough to keep you moving in a northerly direction. But what if you don’t want to go north, but east or west instead?

This is simpler than you might think: as long as you keep the Pole Star on your right, you will be travelling west. Conversely, by keeping the Pole Star to your left, you will be travelling east. However, deviating from east or west is also easier than you might think, but there is a simple way to keep a check on this.

Remember that even though the Plough rotates around the Pole Star in an anti-clockwise direction, the relationship between it and the Pole Star never changes. The same two stars in the asterism will always point to the Pole Star, which will always be the same distance away. So, once you have located north, mark that position on the horizon with a tree, mountain top, or other handy feature to serve as a beacon to keep to your left or right as you move along.

Use Cassiopeia as well

If you are not sure that you have identified the Pole Star, you can always use the “W” shape of the constellation Cassiopeia to confirm that you have located the correct star. The central star in Cassiopeia will always point to the Pole Star as well, so once you have identified the brightest star about halfway between the Plough and Cassiopeia, you can be certain that you have found the Pole Star. The drawing below shows the relationship between the Plough, the Pole Star, and Cassiopeia.

Image credit:
Image credit:

How to find South in the northern hemisphere

Finding south in the northern hemisphere is a little more problematic, but one way of doing it is to use the constellation Orion, which is visible from both hemispheres. The image below shows the relationship between Orion’s “belt”, and the “sword” that hangs from it.

Image credit: Smart Bushcraft
Image credit: Smart Bushcraft

The line formed by the “belt” forms the closest thing to a straight line between any three stars in the sky, so you can hardly miss it. Nonetheless, the “sword” needs to point down to the horizon in a vertical line, which does not happen when the constellation is low on the horizon. So if you can spare the time, wait for the constellation to rise until the “sword” hangs straight down. When it does, a line drawn along the “sword” to the horizon will mark south.

Be aware though that the more the “sword” deviates from the vertical, the further off from south you will be, but you can always “fix” this by referring back to the point on the horizon that marks north.

One more thing

Bear in mind that no form of navigation that uses nature is ever 100% accurate, and the best you can hope for is to find an approximate direction. Moreover, moving through a wilderness area at night is inherently dangerous, so use common sense when doing so, and only use the methods described here when there is no other way of getting out of a predicament.