Why Do Watches Have Moonphases? | Usefulness and How it Works

Have you ever wondered why moon phase watches are synonymous with high end luxury brands and dress watches. When it boils down to utility, there is not really much use to it, is there?

Moon phase watches have always been a fascination to us, in particular the vintage moon phase watches. However, apart from aesthetic reason, is there really a use for moon phase watches?

Uses of Moon Phase in the Past

1) Simple indicator of luminescence at night

2) Tidal Information

3) Principle unit of time - Payments, Taxes etc

4) Astronomy

Seeing as how the moon provides useful information for people, it is understandable why so many vintage watches came with a moon phase complication, and really incredible watches at that.

Zodiac Moonphase Black Dial

In modern times, there are so many more tools that are able to provide a more accurate measure for each purpose, like to find information on tide, a smart phone is easily available, and lighting is so often taken for granted that natural moon lighting is no longer used. However, this does not stop watch manufacturers like Rolex, Patek or even Seiko from still making moon phase watches. As a matter of fact, Rolex just released their Cellini with moon phase in Basel 2017. Present day moon phase complications in all honesty has one use and one use only - it just looks great, and for watch powerhouses, it is to showcase their ability to make top of the line complications.

Moon Phase Components:

- Rotating moon disc with 2 identical moons painted

- Semi circle dial aperture to identify waxing and waning phases

- 59 toothed gear/135 toothed gear

- Mechanical finger

Components of on a moonphase watch - Apertures and disc

How a Moon Phase Watch Works:

- Moon disc sits on the toothed gear (59 for less accurate, 135 for greater accuracy)

- Toothed gear advances 1 notch every 24 hours

- Gear is pushed by the mechanical finger, and one full rotation corresponds to a full lunar cycle (29.53 days)

- A 59 tooth gear can only achieve accuracy of 29.5 days, while a 135 tooth gear will only have a discrepancy of 2.25x10^-5 days.

Therefore, with accuracy in mind, it has been a constant show of capabilities between watch makers to proof that they have the best moonphase, and to date, Ochs and Junior has the most accurate moonphase created, with 3478.27 years of precision and more impressively is only made out of 5 parts for the complication.

Och & Junior Moonphase Components & GearsCredits: Hodinkee

It is clear that, apart from people with chronic Lycanthropy, a moon phase complication is not the most purposeful, however wearing a watch goes beyond simply utility. As a matter of fact, i may wear a watch all the time but check the time on my iPhone.

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