6/17/21
AIM
c. Information on Moon Phases and Changes in
then back through partially illuminated to not
the Percentage of the Moon Illuminated
illuminated again. There are eight distinct, tradition-
ally recognized stages, called phases. The phases
From any location on the Earth, the Moon appears to
designate both the degree to which the Moon is
be a circular disk which, at any specific time, is
illuminated and the geometric appearance of the
illuminated to some degree by direct sunlight. During
illuminated part. These phases of the Moon, in the
each lunar orbit (a lunar month), we see the Moon’s
sequence of their occurrence (starting from New
appearance change from not visibly illuminated
Moon), are listed in FIG 10
−
2
−
3.
through partially illuminated to fully illuminated,
FIG 10
−
2
−
3
Phases of the Moon
New Moon
−
The Moon’s unilluminated side is facing the Earth. The Moon is not visible
(except during a solar eclipse).
Waxing Crescent
−
The Moon appears to be partly but less than one
−
half illuminated by
direct sunlight. The fraction of the Moon’s disk that is illuminated is increasing.
First Quarter
−
One
−
half of the Moon appears to be illuminated by direct sunlight. The
fraction of the Moon’s disk that is illuminated is increasing.
Waxing Gibbous
−
The Moon appears to be more than one
−
half but not fully illuminated by
direct sunlight. The fraction of the Moon’s disk that is illuminated is increasing.
Full Moon
−
The Moon’s illuminated side is facing the Earth. The Moon appears to be
completely illuminated by direct sunlight.
Waning Gibbous
−
The Moon appears to be more than one
−
half but not fully
illuminated by direct sunlight. The fraction of the Moon’s disk that is illuminated is
decreasing.
Last Quarter
−
One
−
half of the Moon appears to be illuminated by direct sunlight. The
fraction of the Moon’s disk that is illuminated is decreasing.
Waning Crescent
−
The Moon appears to be partly but less than one
−
half illuminated by
direct sunlight. The fraction of the Moon’s disk that is illuminated is decreasing.
Special Operations
10
−
2
−
9