Did you know that you can use the stars to tell directions at night? The North Star, or Polaris, is usually within 1-2 degrees east or west of true north. Polaris is at the top of the handle of the Little Dipper, a constellation that is easy to find in the Northern Hemisphere.

You can also use the North Star to determine latitude in the Northern Hemisphere. Use an astrolabe, an instrument to determine the altitude of objects above the horizon, to find your latitude. You can make your own simple astrolabe using a protractor, plastic straw, 12-inch piece of string, and a metal weight (a small bolt or a washer works well). Tie one end of the string to the hole in the middle of your protractor. (If there is not a hole, drill one in the center of the flat-edged piece on the protractor.) Attach the weight to the other end of the string. Now, tape the straw along the flat edge of the protractor.

Locate Polaris, then use your astrolabe to find its altitude. Sight the star through the straw and note what degree the string lines up at on the protractor. (Read the inner set of numbers, from 0-90 degrees.) This number is the zenith angle. To find the altitude angle, subtract the zenith angle from 90 degrees. This number will be the same as, or very close to, the latitude at your sighting location.

For around two thousand years now, people have been using astrolabes for navigation. The Greeks are credited with inventing the instrument. Moslems were using astrolabes by the eighth century, and in 1381 the English author Geoffrey Chaucer wrote a Treatise on the Astrolabe. But the astrolabe’s heyday was in the navigational boom of the 1400 and 1500s. Now the Global Positioning System has eliminated the need for navigation by the stars, except perhaps in emergency situations, but it is still an interesting skill to know.