First Quarter


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Day of Lunar Cycle


Synodic Position

Eastern Quadrature

Angle of Sun-Earth-Moon

The Moon has fallen exactly 90° behind (eastward) the Sun

Illuminated side

Half-turned away from Earth

Near side

Half dark, half light (often called a "half moon")

Overlap between near side and illuminated side


Proportion of whole Moon that is both illuminated and near

25% (therefore a "quarter moon").
Note: This phase is called the "First quarter" because the Moon has traveled one-fourth of its way through the lunar cycle.

Which part of the near side is illuminated?

Westward or Right side (facing south)

Where visible at sunset?

High overhead in the south, crossing the meridian

Where visible at midnight?

Setting in the west.

Where visible at sunrise?

Not visible; near one's nadir.

Where visible at noon?

Rising in the east.

Meridian Transit


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