Coordinates of the subsolar point
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The subsolar point moves constantly on the surface of the Earth, but for any given time, its coordinates, or latitude and longitude, can be calculated as follows:[2]
where
is the latitude of the subsolar point in degrees,
is the longitude of the subsolar point in degrees,
is the declination of the Sun in degrees,
is the Greenwich Mean Time or UTC, in decimal hours since 00:00:00 UTC on the relevant date
is the equation of time in minutes.
Observation in specific locations
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On this azimuthal equidistant projection centred on Mecca, when the subsolar point is on the Ka'bah, shadows of vertical poles on the sunlit hemisphere point away from it
Approximate subsolar point dates vs latitude superimposed on a world map,
the example in blue denoting Lahaina Noon in Honolulu
- ^ Ian Ridpath, ed. (1997). "subsolar point". A Dictionary of Astronomy. Oxford; New York: Oxford University Press. ISBN 0-19-211596-0.
The point on the Earth, or other body, at which the Sun is directly overhead at a particular time.
- ^ Zhang, Taiping; Stackhouse, Paul W.; MacPherson, Bradley; Mikovitz, J. Colleen (2021). "A solar azimuth formula that renders circumstantial treatment unnecessary without compromising mathematical rigor: Mathematical setup, application and extension of a formula based on the subsolar point and atan2 function". Renewable Energy. 172: 1333–1340. doi:10.1016/j.renene.2021.03.047. S2CID 233631040.
- ^ Nancy Alima Ali (May 11, 2010). "Noon sun not directly overhead everywhere". Honolulu Star-Bulletin. Retrieved November 12, 2010.