Index   586 -- Page 587 -- 588

12/10/15                                                                                                     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-
From any location on the Earth, the Moon appears to       ally recognized stages, called phases. The phases
be a circular disk which, at any specific time, is        designate both the degree to which the Moon is
illuminated to some degree by direct sunlight. During     illuminated and the geometric appearance of the
each lunar orbit (a lunar month), we see the Moon's       illuminated part. These phases of the Moon, in the
appearance change from not visibly illuminated            sequence of their occurrence (starting from New
through partially illuminated to fully illuminated,       Moon), are listed in FIG 10-2-3.

                                                   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