Observing Solar Cycles Using Sundials
Equatorial Sundial Gnomon Length CalculatorUse the following rule-of-thumb to determine the length of the upper segment of the gnomon: "If the shadow of the gnomon is to reach the circle of hour numbers at the times of the solstices, the gnomon must be about half as long as the radius of that circle. (The theoretical value is 0.44 times the radius.)" Quote courtesy Sundials: Their Theory and Construction, Albert E. Waugh, Dover Publications, Inc., ©1973, p. 32. Input the radius of the dial plate (one-half the diameter) and your latitude to calculate the length of the lower segment of the gnomon required to properly orient your equatorial sundial.
Note that the computer is unable to display infinity (¥) properly.
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