Analemmatic sundial

Analemmatic Sundial

Analemmatic sundial

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Description:
<!-- These images show the analemma- but are not analemmetic dials- where the gnomon is moved to a particular spot on the analemma --read the references given below

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Analemmatic sundials are a common feature at science museums , planetariums and occasionally in public places. They exploit the fact that the sun travels in a predictable pattern over the course of a year called the analemma and trace the projection of an object's shadow to measure time, not only the hours, as in normal sundials, but also weeks and months.

Description

Accurate dials of this type are popular in public places, using a ball at the tip of a flagpole as the nodus, with the sundial face painted on or inlaid in the pavement. A less accurate version of the sundial is to lay out the hour marks on a pavement, and then let the user stand in a square marked with the month. The user's head then forms the gnomon of the dial. In middle latitudes, the ellipse with the hour-marks will be about six meters wide, so the shadow of the head of the beholder falls near it most of the time.

Construction

An analemmatic sundial uses a vertical gnomon and its hour lines are the vertical projection of the hour lines of a circular equatorial sundial onto a flat plane.Rohr (1965), pp. 100&ndash;106; Waugh (1973), pp. 108–115; Mayall and Mayall, p. 60–61,...
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