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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

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3. 

through partially illuminated to fully illuminated, 

FIG 10

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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 

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