The subsolar point: where the Sun is overhead at an instant. Its latitude is the Sun's declination and its longitude follows the Sun's hour angle from Greenwich; the day/night terminator is the great circle 90 degrees from it.
The subsolar point: where the Sun is overhead at an instant. Its latitude is the Sun's declination and its longitude follows the Sun's hour angle from Greenwich; the day/night terminator is the great circle 90 degrees from it.