The moon is only in this position for a single instant in the whole lunar month: the exact time of the full moon, when it is 180 degrees away from the sun. The rest of the month it can be anywhere from 0 to180 degrees away and, at least in theory, visible in the daytime sky. At full moon, the moon is exactly opposite the sun. This means that the moon rises just as the sun is setting, and sets just as the sun is rising.
The main reasons for moon visibility in daylight are:
- it is bright enough that its light penetrates the Scattered blue light of the sky.
- The moon must be high enough in the sky to be visible.