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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 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.).