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 August.
At New Moon, the Moon behaves like the Sun in August.
The
crescent Moon behaves like the Sun in autumn. It's heading
southwards, so it spends less time above the horizon every day. The
time of moonrise gets much later every day; the time of
moonset doesn't change much from one night to the next, but the
position of moonset shifts southwards (left) along the horizon.
The
First-Quarter Moon behaves like the Sun in November (3 months
forward).
The waxing gibbous Moon behaves like the Sun in
winter. It only spends a few hours each day above the horizon, rising
in the south-east and setting in the south-west.
The Full
Moon behaves like the Sun in February (opposite to the August Sun).
The waning gibbous Moon behaves like the Sun in spring. It's
moving northwards, so it spends longer above the horizon every day.
The time of moonrise doesn't change much from one night to the next,
but the position of moonrise shifts northwards (left) along the
horizon.
The Last-Quarter Moon behaves like the Sun in May (3
months ago).
The waning "crescent" Moon behaves
like the Sun in summer. It is above the horizon for many hours of
each day, rising in the north-east and setting in the north-west.
On any date, if you know how many
days it is since New Moon:
multiply that by twelve, and add it to the present date, to find out
roughly where the Moon will be in its cycle.
However, the Moon doesn't follow the
Sun's path exactly. To find out what
difference that makes, try clicking here.
Return to
"What is the Moon doing?"
Return to
"What's in the Sky"
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