maansstanden

Maansstanden refers to the appearance of the illuminated portion of the Moon as seen from Earth, collectively known as the Moon's phases. They arise from the changing relative positions of the Sun, the Moon, and the Earth during the Moon's orbit. As the Moon travels around Earth, different parts of its sunlit hemisphere are visible, creating a repeating cycle known as the synodic month.

The cycle lasts about 29.53 days, though the Moon completes a sidereal orbit (~27.3 days) in between. The sequence of principal phases is: new moon, first quarter, full moon, and last quarter. Between these, the Moon appears as a waxing crescent, waxing gibbous, waning gibbous, and waning crescent. The terms waxing and waning describe whether the visible illuminated portion is growing or shrinking.

The precise appearance and timing of each phase depend on the observer's location and the Moon's position relative to the Sun. The Moon rises and sets about 50 minutes later each day, and its phase is independent of local sunrise or sunset. In practice, the phase is most noticeable when the Moon is high in the sky and contrast is strong.

Maansstanden have been used in calendars, tides, navigation, agriculture, and ritual practices across cultures. Modern astronomy tracks them with ephemerides and software, which predict exact times of moonrise, moonset, and every phase.