Humankind has been obsessed with tracking the sun, the moon, and the stars for millennia. That’s why we have timepieces in the first place. While tracking the sun allowed our ancestors to follow the passing of time, days, and seasons, reading the phases of the moon was one of the only ways to track the passing of months. This makes the moonphase one of the oldest complications in the history of horology.
In this article, we will discuss what makes a moonphase watch special, how it works, and why you might want one for yourself!
What Is a Moonphase Watch?
Strictly speaking, a Moonphase watch is one that possesses a complication that tracks the 29.5-day cycle between full moons. The mechanism to track the phases of the moon predates watchmaking entirely. The earliest example was discovered in a Greek shipwreck in 1901 and dates back over 2000 years!
The earliest known example of a moonphase was the Antikythera mechanism. The artifact was found off a shipwreck in the Greek island of Antikythera in 1901, but studies showed it dates back to 2nd Century BC. Photo: NAMA Machine d’Anticythère, by Marsyas, licensed by CC BY 2.5
When the moon has played such a great role in humankind’s existence, why wouldn’t we still feel the need to track it today? From religious holidays, to harvest season and navigation, it’s always been a priority to track through the phases to some degree or another.
The more complicated pocket watches of the 19th and 20th centuries often tracked the phases of the moon. It makes sense that when watchmakers shifted over to wristwatches for men as well as women, that the tracking of the phases of the moon followed too.
Two Styles of Moonphase Watches
There are two styles of moonphase watches the most common being the bosom moonphase watch. This is probably the type you’re most familiar with. An aperture in the watch dial reveals the parts of the moon that are currently visible in the night sky.
The other, less popular style of moonphase is the radial moonphase watch. This type of watch uses an indicator hand to show the current phase of the moon.
Bosom Moonphase (left) versus Radial Moonphase (Right). Blancpain Villeret Complete Calendar 8 Days and Jaeger Lecoultre Master Grande Reveil
The earliest mechanism used on watches to display the phases of the moon was a simple dial with two pictorial representations of the moon on either side. A 59-tooth driving wheel turned the dial once per day. After 29.5 days a full lunar cycle is completed, and the second moon would appear in the aperture on the dial.
Accuracy of Moonphase Watches
The standard 59-tooth wheel is consistently accurate, but still limited in the actual precision. In actuality, the moon cycle is precisely 29 days, 12 hours, and 44 minutes or 29.53 days. As such, your watch is missing 0.03 days each month. Eventually, this adds up. You’ll have to manually adjust the watch a full day every two years and seven and a half months. That’s how long it takes your moonphase dial to fall behind a full day. Manually adjusting every three years will be enough to maintain the accuracy of your moonphase watch.Patek Philippe made the first ever moonphase wrist watch – the Perpetual Calendar 97975, introduced in 1925. (photo: Patek Philippe)
Luxury brands have adapted to a 135-tooth wheel for their moonphase dial leading to a considerable boost in the accuracy. These particular watches won’t have to be manually adjusted until 122 years have passed! Not a bad trade off for a slightly more complicated wheel in the movement.
How Does a Moonphase Watch Work?
Moonphase watches display the phases of the moon, and they’re mechanical watches. A rotating disc shows the phases of the moon, which means you can tell when it’s full or new without having to rely on your phone or an app.
The moonphase is the lighted portion of the moon in the sky and the dial on your watch will display it simultaneously.
The moonphase mechanism itself isn’t complicated: It’s just a series of gears that move in relation to one another as time goes by (and when you set your watch).
Jaeger Lecoultre Master Control Perpetual Calendar Rose Gold Watch 140.2.80
Most basic moonphase designs use discs with holes cut out around them. This allows you to see where everything lines up on each day so that you know what phase it should be entering into next — and how far along in its cycle it has progressed since last month’s Full Moon.
Some more complicated moonphase systems use digital readouts or lights that shine through a semi-opaque representation of the moon.
Compared to other complications, it’s not necessarily practical in this day and age, yet they are still incredibly popular. Maybe it’s our historic drive to follow the moon. Maybe it’s innate and in our bones to track the world around us. Either way, they’re a beautiful addition to any watch face.
A few excellent Moonphase watches
Rolex Cellini Moonphase
Rolex Cellini Moonphase White Dial Rose Gold Mens Watch 50535
Rolex Cellini Moonphase watches are a classic example of the moon phase complication on a stunning dress watch. As Rolex is far more known for their sports watches that transcend nicely between casual and dress, the Cellini Moonphase often falls through the cracks unnoticed.
It’s currently the only model in the Rolex catalog without an Oyster case, and with a moonphase dial. Located at 6 o’clock is the prominently displayed blue moonphase dial under the starker white face dial. This particular dial features an image of the full moon and a dark new moon.
Omega Speedmaster Moonphase
Omega Speedmaster Moonphase Chronograph Mens Watch 304.33.44.52.03.001
You can’t have a list of Moonphase watches without including the Omega Speedmaster – the watch that traveled to the moon on all six lunar missions.
That’s not all that makes this watch a wonderful addition to your wrist. The hyper-realistic moon image on the dial tucked behind the crescent aperture at 6 o’clock, draws the eye with the incredible detail. There’s even an oversized footprint marking where the watch landed on the moon the first time.
The moonphase function on this watch only needs to be manually adjusted once every 10 years to maintain accuracy.
Cartier Drive Moonphase
Cartier Drive de Cartier Silver Dial Moonphase Mens Watch WSNM0008
Combine an excellent moonphase complication and a unique case shape and you have a stunning timepiece. Still, with its simplistic style, it’s one of Cartier’s more subdued moonphase watches.
With bold Roman numerals, you’d think the moonphase dial would get lost, but it subtly draws attention to the aperture at 6 o’clock. The stark colors stand out nicely against the silvered guilloche dial. The stylistic aperture makes the moon peak out over a set of white mountain-like shapes.
On this watch, the moonphase takes the show as the only additional dial on the face. The signature Cartier blued steel hands offset the blue of the sky quite nicely.
Patek Philippe Nautilus 5712 Moonphase
Patek Philippe Nautilus Blue Dial Moonphase Steel Mens Watch 5712
The Patek Philippe Nautilus 5712 has the moonphase as the main complication of the watch, but it snuggles nicely inside the date dial. By combining the complications, Patek found an excellent way to declutter the iconic embossed dial. There’s even a small, unobtrusive indicator of the 48-hour power reserve level for the automatic, self-winding movement.
Pairing a gradient blue dial with a stainless steel case, it’s a favorite from the Nautilus line.
Moonphase Watches: Final Thoughts
We hope this article has given you a better understanding of moonphase watches. If you’re interested in purchasing one, we highly recommend checking out our list of some of the best models on the market today at SwissWatchExpo.com.
There’s a reason why the moonphase remains a popular complication, even if it’s no longer the most practical. As such, tracking the moon with your watch has become an art form with each brand finding a way to make it as artistically beautiful compared to the next.