When I really started paying attention to the Sun, stars and Moon many years ago, one of the things that confused me was why the Quarter Moons looked like Half Moons.

The Moon is at or near its last quarter phase tonight, February 6, and into tomorrow morning. (The precise time is tomorrow at 15:54.)  Take a look tonight and you will see half of the Moon. Half the moon always faces us, and half the moon is always lit by the sun, though we can’t see that. To astronomers, there are no ‘half moons.’

So why does this phase get the name Quarter Moon is we can see half of it lit?  First quarter moon means the moon is one-quarter of the way through the current orbital cycle. Tonight’s third or last quarter moon means the moon is three-quarters of the way through the cycle, as measured from one new moon to the next.

moon phases

The phases of the Moon as viewed looking southward from the Northern Hemisphere. Each phase would be rotated 180° if seen looking northward from the Southern Hemisphere. The upper part of the diagram is not to scale, as the Moon is much farther from Earth than shown here. Image: wikipedia.org

It is all about perspective. At first quarter moon, the near side of the moon (the part we see) is half-illuminated by sunlight and half in its own shadow, so we are seeing half the moon’s day side.

It may also seem curious that in the Southern Hemisphere tonight the right side is 50% lit and in my Northern Hemisphere it is the left side that is bright. Yes, when we enter the first quarter that will be reversed.

A third quarter moon always rises in the middle of the night. It will appear at its highest in the sky around dawn, and will set around midday.


To move away from the sky though, I do like the name “Half Moon.” Half Moon Bay is a town on the California coast that I visited once and the name seems kind of romantic. There is a song called “Half Moon Bay” from 1969 by a band that I followed, Mott the Hoople. The lyrics have nothing to do with the town and the Dylan-esque vocals don’t make the lyrics any happier or romantic. It was a song I liked for its Procol Harum-like organ back then – and the album’s Escher cover is still a favorite. (Listen  on YouTube)

Another more recent song with that same title is by Train.  This one is actually about the California town and more “romantic.”

This ain’t a threat but I think I better warn ya’
Gonna fall in love if you go to California
I did and this is how I know
By the beach north of San José
Met the right girl and it sounds cliché
But we decided not to take it slow

But remember, there may be a Half Moon Bay, but there are no half moons.

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