Have you ever heard someone look at the sky and say, “It’s a perfect half moon“?
While the term “half moon” may make sense from a visual perspective when only half the moon’s face is visible, the lunar cycle is actually a bit more complicated than that. The truth is, there’s no such moon phase.
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There’s no such thing as a “half moon” phase
The correct term to describe a half-visible moon is a “First Quarter moon” or a “Last Quarter moon” depending on what part of the lunar cycle the moon is in.
List of moon phases
- New Moon
- Waxing Crescent
- First Quarter
- Waxing Gibbous
- Full Moon
- Waning Gibbous
- Last Quarter
- Waning Crescent
Why isn’t it called a “Half Moon”?
The lunar cycle consists of 8 moon phases, starting from the New Moon. The actual “half way” point of the lunar cycle between New Moons is really the Full Moon.
In order to avoid confusion, the term “half” is not used to describe the appearance of the visible moon.
So what’s a “Third Quarter Moon?”
In some circles, you’ll hear the term “Third Quarter moon” to describe the Last Quarter. Both terms are correct, but “Last Quarter” is more common.
So how can you tell a First Quarter moon from a Last Quarter moon?
Another common question is, how can you tell the difference between a First Quarter and a Last Quarter moon? Visually speaking, they both look like a “half moon”.
It’s a common misconception to think that you can distinguish between the two “Quarter moons” based simply on whether the left side or right side is illuminated. Unfortunately, the side that is on the left and the side that is on the right depends on where you are on the Earth.
If you really want to know whether or not the moon is in its First Quarter or Last Quarter, the easiest way to find out is to check the current moon phase with a moon phase application.