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Pillar Dial /
Shepherd's Dial

Latitude specific, Altitude

The pillar dial, also known as the shepherd's dial, is the portable sundial with the longest continuous history of use.

This dial, like many others, is often made from either wood and paper, ivory, or metal. It features an hour scale that wraps around the body of the dial. Occasionally, the dial will feature a removable cap which holds a gnomon for each half of the year.

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The Sundial Primer

British Museum

Helmut Sonderegger

The Sundial Primer

How to use

1. Remove the dial's cap and prepare the gnomon for use by setting it perpendicular to the dial face. For dials with a summer and winter gnomon, choose the one appropriate for the day of operation.

2. Rotate the gnomon so that it sits above the current date on the dial plate.

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. Each hour curve corresponds with two hours, so the operator must determine in advance whether the reading is being taken before or after noon.

6. To determine civil time, add the appropriate longitude correction and equation of time correction (more information here). If applicable, add one hour during daylight saving time.

Overview of Instrument
Outdoor Demonstration
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