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Canterbury Altitude Dial / Anglo-Saxon Altitude Dial / King's Dial

Latitude specific, Altitude, Seasonal hours

The Canterbury dial is one-of-a-kind; only one example of this type of dial is known to exist. The original was discovered beneath a cloister of the Canterbury cathedral in England.

The dial is designed for a single latitude. It operates using seasonal hours, but only displays three–the third, sixth, and ninth hours.

Depending on the month of use, the pin gnomon is inserted into one of the dial's six holes across its two faces. Each hole is used for two months of the year. When the dial is suspended and oriented so that the shadow of the gnomon falls directly below it, the seasonal hour can be read.

 

The dial is quite small, able to be worn around the neck while not in use. This dial can be seen as a close relative of the pillar or shepherd's dial, as both are altitude dials which use protruding gnomons to cast shadows on their hour surfaces. Both dials also require that the gnomon be adjusted to a new position for each month of the year.

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How to use

1. Unfasten the pin gnomon from its chain.

2. Locate the current month, and insert the gnomon into the corresponding hole.

3. Suspend the dial, leveling it to the local horizon.

4. Point the gnomon to the current azimuth of the sun and ensure that the gnomon's shadow falls directly beneath onto the hour scale.

5. Read the position of the shadow on the scale. At the third hour, the shadow will land on the first dot; at the sixth hour, the shadow will land on the second; at the ninth hour, the shadow will again land on the first mark.

Overview of Instrument
Outdoor Demonstration
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