Noon mark

Noon mark
A noon mark on the facade of the Palais des ducs de Bourgogne in Dijon

The Noon mark is a type of sundial that at its simplest is a vertical line on a south facing wall. When the shadow of a point passes over the line it will be midday. 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.[1]

References

Notes

  1. ^ Waugh 1973, pp. 18–28

Bibliography

  • Mayall RN, Mayall MW (1994). Sundials: Their Construction and Use (3rd ed.). Cambridge, MA: Sky Publishing. ISBN 0-933346-71-9. 
  • Hugo Michnik, Theorie einer Bifilar-Sonnenuhr, Astronomishe Nachrichten, 217(5190), p. 81-90, 1923
  • Rohr RRJ (1996). Sundials: History, Theory, and Practice (translated by G. Godin ed.). New York: Dover. ISBN 0-486-29139-1.  Slightly amended reprint of the 1970 translation published by University of Toronto Press (Toronto). The original was published in 1965 under the title Les Cadrans solaires by Gauthier-Villars (Montrouge, France).
  • Waugh AE (1973). Sundials: Their Theory and Construction. New York: Dover Publications. ISBN 0-486-22947-5. 
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