Lunar Phases

The Moon is not illuminated by the Sun equally during its movement around the Earth. The shape of the illuminated portion of the Moon as seen by an observer on Earth we call lunar phase. The lunar phases change periodically. We see the same lunar side from the Earth.



We distinguish eight typical lunar phases. In fact, more often we tend to say only about the four principal lunar phases. They are the New Moon, First Quarter, Full Moon, and Third Quarter. The difference between the observation of these phases are visible the most in the first and third quarter phase. In the first one we observe the right side of the Moon illuminated. The illuminated right portion of the Moon means for the observer in the Northern hemisphere that the part is always growing. If the right side of the Moon is dark (third quarter) then the light part is shrinking, and the Moon is referred to as Waning. In the Southern hemisphere the Moon is observed from a perspective inverted to that of the Northern hemisphere.