What is the Moon doing in December?
The Moon in December
In general, we can tell what the Moon will look like, when it will be visible, and in what direction to look for it, just by working out how many days it is since New Moon. The details are here.
But we can predict this more accurately by noticing that the Moon mimics, every month, the way the Sun behaves over the course of a whole year.
Here is a schematic diagram of how the Moon behaves in December.
Just after New Moon, the crescent Moon behaves like the Sun in January. It's still far to the south, so it spends very little time above the horizon each day. It rises in the south-east and sets in the south-west.
But now the Moon is starting to move northwards again. The time of moonrise doesn't change much from one day to the next, but the time of moonset gets later every evening. So we have an increasingly good chance of seeing the Moon in the southern sky after sunset. By First Quarter, the Moon is above the horizon for 12 hours out of the 24, rising due east and setting due west.
As the Moon waxes through gibbous, it continues to head northwards, staying up later every night. By Full, the Moon has reached its northernmost point, and it's behaving like the Sun at midsummer, in June: the Moon rises in the north-east as the Sun sets in the south-west, and it stays above the horizon all through the long hours of darkness.
As it wanes, the Moon is moving southwards again, like the Sun in autumn; moonset doesn't change much from one night to the next, but moonrise gets much later every night. In the days before New Moon, we can only glimpse the Moon at sunrise, coming up in the south-east. But it's still further north than the Sun, so we should be able to see it almost all the way up to New Moon.
However, the Moon doesn't follow the
Sun's path exactly. To find out what
difference that makes, try clicking here.