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A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat plate (the dial ) and a gnomon , which casts a shadow onto the dial.
Burt's solar compass or astronomical compass/sun compass is a surveying instrument that makes use of the Sun's direction instead of magnetism. William Austin Burt invented his solar compass in 1835. The solar compass works on the principle that the direction to the Sun at a specified time can be calculated if the position of the observer on the ...
The Sunquest Sundial is a sundial designed by Richard L. Schmoyer in the 1950s. Adjustable for latitude and longitude, the Sunquest's gnomon automatically corrects for the equation of time allowing it to tell clock time. The Sunquest sundial utilizes a cast aluminum gnomon, the shape of which is related to the analemma. When turned to face the ...
A sundial on a gravestone in Kilbirnie Auld Kirk, Kilbirnie, Ayrshire, Scotland. The motto at top reads, The motto at top reads, "Life is but a passing shadow, the shadow of a bird on the wing."
The gnomon is the triangular blade in this sundial. A gnomon (/ ˈ n oʊ ˌ m ɒ n,-m ə n /; from Ancient Greek γνώμων (gnṓmōn) 'one that knows or examines') [1] [2] is the part of a sundial that casts a shadow. The term is used for a variety of purposes in mathematics and other fields, typically to measure directions, position, or time.
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. [6] Therefore, the analemmatic sundial is an ellipse , where the short axis is aligned north–south and the long axis is aligned east–west.
A digital sundial is a clock that indicates the current time with numerals formed by the sunlight striking it. Like a classical sundial, the device contains no moving parts. It uses no electricity nor other manufactured sources of energy. The digital display changes as the sun advances in its daily course.
Noon in local standard time is defined as when the sun is overhead, however clocks and watches use mean time which varies from standard time by a few minutes each day. The difference is calculated using the equation of time and this can be shown on the noon mark by drawing an analemma , or using a correction table.