Bridge Learning Center

Parts of a Sundial

A compass rose (usually on a horizontal dial) shows the azimuth of the sun.

Mottos, sayings or poems included on the dial (a popular example is Tempus Fugit QuoQue Serpit).

Analemmas show the relation between the equation of time and the Suns declination.

A Sundial for Reutte

A Sundial design contest was announced for Reutte, Austria. The closing date for an entry was 9/25/1998. The judging date was 10/3/1998.

Most sundials that are available (science shops, garden shops etc.) are not going to work without a little adjusting.

Many of these "popular" horizontal dials have a gnomon which is 45 degrees. As we know this means that this dial was, hopefully, designed for a latitude of 45 degrees (like Minneapolis, MN). Make sure by measuring the angle of the gnomon.

The gnomon needs to point to the North Celestial Pole (true North) so unless the angle of the gnomon is equal to the latitude the horizontal dial must be "tipped".

If the gnomon was measured to be 45 degrees, but the latitude is 30. Then there is a difference of -15 degrees between the gnomon and the latitude. So we must tip the whole dial so the the gnomon is lowered 15 degrees. If the latitude was greater than the angle of the gnomon then we would tip the whole dial so the gnomon is raised the correct amount.

These adjustments will correctly adjust for one latitude any properly constructed horizontal dial for a different latitude.

A serious sundial link(s) page !
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