A week after New Moon, the Moon reaches its First Quarter. In this phase, the Moon is in quadrature (elongation = 90o, position C in the diagram below), and one half of the Moon's disk is illuminated as seen from Earth. The First Quarter Moon rises at noon, transits the meridian at sunset and sets at midnight.
What does First Quarter of the moon mean?
Filters. The phase of the moon at which the moon, as viewed from Earth, appears to be half illuminated by the sun on its westernmost side. noun.
What is the First Quarter phase of the moon called?
The First Quarter Moon is also called a Half Moon because the Sun's rays illuminate exactly 50% of the Moon's surface. Half of the Moon's surface is always illuminated by direct sunlight, except during lunar eclipses when Earth casts its shadow on the Moon.
