Land navigators can use star navigation to find their way overland at night. In many instances while on foot in the wilds, it's better to stay put after dark, and navigate only during the daylight, considering that the chance for injury goes up after dark. The notable exception to this is desert travel, in which it sometimes makes more sense to travel in the cool of night rather than in the blazing heat of the day. And, of course, if you're in the military, you're called on to travel at all hours.
If you must navigate at night, of all our celestial guideposts--the sun, the moon, and the stars--the stars are, in my opinion, the easiest to navigate by.
How the Stars Work
Although the stars move throughout the night sky, they are fixed in relation to one another. This discussion doesn't include planets, which do move in relation to other celestial bodies. Instead, it focuses only on stars, and only on those relatively few stars and star patterns suitable for navigation.
Stars of the Northern Hemisphere
To picture the northern hemisphere's stellar clockworks, imagine holding a giant umbrella out in front of you. Now, imagine small stars glued to the umbrella's underside in the same relation to one another as you'd find in the night sky. In the exact middle of the umbrella is the pole star, otherwise known as Polaris, or the North Star. Slowly twirl the umbrella in a counterclockwise fashion, causing all the stars fixed to the umbrella to revolve around the pole star.
The umbrella gives us a good analogy for the apparent star movement in the northern hemisphere's night sky. Actually, the stars don't move, the earth does, causing the stars to appear to move. But to simplify things, I'll explain star workings from the perspective of the earthbound observer.
Directions by Star Patterns
For navigation purposes, it's highly convenient that the stars are fixed in relation to one another. This means that while the star patterns we see in the night sky change position as the stars slowly revolve counterclockwise around Polaris, the patterns themselves don't change.
People have been observing these unchanging star patterns for centuries. Just as you've no doubt identified here and there imaginative shapes in fleeting cloud patterns, people over the centuries have identified imaginative shapes among the stars--a dipper, a charioteer, a hunter, a lion, and so on.
Some of these imaginative star patterns--these constellations--have proven to be very useful for navigation purposes.
If you have a sextant or some other precision instrument, you can find your position within a couple of miles or so. That's a pretty cool thing to be able to do, even in the GPS age, but what we'll concern ourselves with here is not finding position, but finding direction by the stars. That's a cool thing to be able to do too, especially if you find yourself having to travel in the wilds at night with no compass. Even if you do have a compass, it's reassuring to know it's correct by double checking it with the stars.
Okay, so which stars and star patterns here in the northern hemisphere are useful to us?
Find the complete grouping on my Celestial Navigation page.
Stars of the Southern Hemisphere
The Southern Hemisphere has no central pole star around which all the others revolve. (Don't we wish it did?) But that doesn't mean we can't navigate by stars on the earth's underside. While there's no southern-hemisphere equivalent of Polaris, there is the prominent Southern Cross that can help us locate the sky's south pole--that central blank point in the southern sky around which all the other stars revolve.
Looking south to the sky's pole while in the southern hemisphere, you'll see that all the stars circle the pole in a clockwise fashion. They're still going in the same direction--from east to west--as they do in the northern hemisphere, but looking south, an east-to-west direction is clockwise, while looking north that direction is counterclockwise.