Subsolar point

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]

$${\displaystyle \phi _{s}=\delta ,}$$

$${\displaystyle \lambda _{s}=-15(T_{\mathrm {GMT} }-12+E_{\mathrm {min} }/60).}$$

where

• ${\displaystyle \phi _{s}}$ is the latitude of the subsolar point in degrees,
• ${\displaystyle \lambda _{s}}$ is the longitude of the subsolar point in degrees,
• ${\displaystyle \delta }$ is the declination of the Sun in degrees,
• ${\displaystyle T_{\mathrm {GMT} }}$ is the Greenwich Mean Time or UTC, in decimal hours since 00:00:00 UTC on the relevant date
• ${\displaystyle E_{\mathrm {min} }}$ is the equation of time in minutes.

• Qibla observation by shadows, when the subsolar point passes through the Ka'bah in Saudi Arabia, allowing the Muslim sacred direction to be found by observing shadows.
• When the point passes through Hawaii, which is the only U.S. state in which this happens, the event is known as Lahaina Noon.[3]

Approximate subsolar point dates vs latitude superimposed on a world map, the example in blue denoting Lahaina Noon in Honolulu

• Subsatellite point

• Day and Night World Map (shows location of subsolar point for any user-specified time)