NOVA Online | Shackleton's Antarctic Odyssey

Making an Astrolabe

Using scissors, cut out the astrolabe silhouette (heavy black lines) on this sheet.
Tape this silhouette onto your manila folder sheet and cut out this figure.
Make a tiny hole at the index point (marked by an "X"), push the end of a 7-inch piece of string through the hole and tape that end to the backside of the cardboard. Attach a paper clip to serve as a weight at the other end of the string that falls over the degree markings on the front of your astrolabe.
Fold the cardboard along the dashed line as indicated on the diagram so that the sides with the triangular notch form a right angle with the face of the astrolabe. Make sure the sides are still at a right angle at night when you use the astrolabe.
Take your astrolabe home to use at night. Using a star map, locate the Big Dipper, which will point you to the star Polaris. Face Polaris and raise your astrolabe until you can sight Polaris through both notches. Make sure that the paper clip and string are hanging straight down (i.e., do not tilt the cardboard as you sight on Polaris; the astrolabe must be perpendicular to the ground).
When you can see Polaris throught both notches, press the string against the cardboard and record the angle at which the string crosses the scale. This angle is the altitude of Polaris, which is also your latitude value.