Moon cycle and phase

In 29.5 days the Moon completes a full cycle of phases. This is called the Lunar Cycle or synodic month. This Lunar cycle originally inspired the concept of what we now call a month. Month lengths in some historic calendars followed motions of the moon.
But our calendar's irregular distribution of days in the various months no longer corresponds to the lunar cycle. Our present day calendar follows the seasons which are caused by the annual motion of the Earth around the Sun. Therefore Moon phase and day in the month are not related.

Find the Moon Phases for this month (or any other month) here (thanks to Arthur's Pass Mountaineering)

Names of the Moon Phases
When the illuminated part of the Moon appears smaller than half the Moon disk, it is called a crescent; when it appears larger, it is called gibbous. If it is precisely a half disk it is called a quarter.
When the illuminated part of the Moon is growing it is waxing. When it is getting smaller it is waning.

How do we know if the Moon is waxing or waning?
If the crescent Moon looks like a "C" it is growing, when it looks like a capital "D" it is waning.

But be mindful that this is the situation for the Southern Hemisphere. On the Northern Hemisphere it is the other way around. That is because people on the Northern Hemisphere are "upside down" as compared to us in the south. Although the northerners would probably prefer to say that we are "upside down", hence the term "down under". Anyway, when you are in the Northern Hemisphere, you will see the constellations and the Moon phases the other way around than we see them here in the south. After all, there is no up and down in space, is there?

To find out more about our Calendar system or the Moon and its phases, sign up for our next course Astronomy I.

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