出典:Wiktionary
noonmark (複数形 noonmarks)
出典:Wikipedia
出典:『Wikipedia』 (2011/05/16 17:57 UTC 版)
The Noon mark is a type of sundial that at its simplest is a 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.