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How To Tell If You Are Looking at a Full Moon

A lot of people see a big round moon in the sky and confidently call it a full moon. And then wonder, is it really?

How can we tell if the moon we are looking at is indeed a ‘full moon’?

There are 3 methods that work well when used together:

  1. A full moon does appear round, as a full circle. But a lot of moons that look like circles are not actually full. The reason is that the moon looks very close to round either side of full moon. So, seeing a round moon does tell us that we are very close to a full moon, but doesn’t guarantee that it is full.
  2. Full moons are full because they are opposite the sun. And this gives us our biggest clue: full moons are extraordinarily bright. Much brighter than the round moons we see a day either side of full.
  3. Full moons rise near the time the sun sets (because they are opposite the sun.)

None of these methods on its own works perfectly, but together they work well.

A perfectly round, extraordinarily bright moon that rises close to the time of sunset is probably full.

Did you know:

A couple of days after a full moon, the tides reach their maximum range, known as spring tides.

In winter, full moons rise north of east, in summer they rise south of east.

Full moons are close to due south at midnight.

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