When the sun, earth , and moon are in these positions, what phase of the moon do we observe?

First Quarter: When the Earth-Moon line is

90

o

away from the Earth-Sun line, it is the First Quarter phase. On those days Moon rises (approximately)

6

hours after the Sun rise and exactly one quarter of the Moon's surface is visible from Earth.

[3] Full Moon: Moon, Earth and Sun lined up with the Earth coming between the Moon and the Sun. But usually the alignment is not perfect with the Moon's longitude lying a little above or below the Sun's longitude. The Earth-Moon line and the Earth-Sun line are close to

180

o

away. However, occasionally the alignment could be near perfect leading to an eclipsing of Moon by the Earth. That is Lunar Eclipse . Not every Full Moon is a Lunar Eclipse but every Full Moon coincides with a Full Moon. On Full Moon days Moon rises just as the Sun sets.

[4] Third Quarter: When the Earth-Moon line is

270

o

away from the Earth-Sun line, it is the Third Quarter phase. On these days Moon rises (approximately) 18 hours after the Sun rise or (approximately)

6

hours after the Sun set and again exactly one quarter of the Moon's surface is visible from Earth.

Explanation: