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The Viking Sun Compass
No Viking would leave on a voyage of exploration or conquest without their trusty Sun Compass.

The Viking Sun Compass is an ingenious device which allows the navigator to know where North was and, therefore, what direction he was sailing.

The Sun compass is essentially a sundial used in "reverse". Imagine a circular wooden disk about 4 or 4 inches in diameter set level to the ground. From the center rises a thin post or gnomon. When the sun is out, the gnomon casts a shadow on the disk. Were you to mark the position of the tip of the shadow each half an hour, and then connect the points, you would generate an arc. That arc is a recording of the sun's height during the day, at that time of year, at that latitude. If you drew a line from the center of the gnomon, to the point on the arc that was closest to the gnomon, you will have defined True North on the sun compass. From there you can mark out the rest of the 32 points of a compass. Now you've calibrated the Sun Compass. To use the compass you shove off to sea and wait for a sunny day. You must know whether it's morning or the afternoon. Once you know that, if you hold the Sun Compass completely level, and then spin the disk about it's axis (about the gonomon) there is one and only one point where the tip of the shadow cast by the gnomon touches the curve you drew. The compass is now oriented. You now look at the compass marks to determine which direction is North (or South etc.).

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