Moon phases are one of the most prevalent complications in watches. Humanity has always been fascinated with the heavens above, so it’s no surprise that watchmakers found a way to capture the moon’s beauty in a watch. Moon-phase watches range from métiers d’art masterpieces to complicated calendars and elegant dress watches.
Many watchmakers use the moon-phase disk to showcase their métiers d’art. Mother-of-pearl and aventurine are frequent materials because glittering blue aventurine evokes a starry night sky. The texture and shimmer of mother-of-pearl represents the craters on the glowing moon. Other techniques include using hammered metal for the moon, painting the moon, or using enamel. Clouds and stars frequently decorate the disk, too.
Here, we explain everything you need to know about how moon phases work and showcase the finest luxury moon-phase watches.
How Does a Moon Phase Work?
As its name suggests, a moon phase shows the phase of the moon, which is the moon’s illuminated area. Typically, there’s a disk underneath the dial decorated with two moons. The dial has a window that the disk peeks through. The disk rotates accordingly as the moon moves through its 29.5-day cycle as seen from Earth. At first, just a small sliver will show, indicating a waxing crescent moon. The moon will grow larger until it’s completely revealed at the full moon. The disk continues to rotate, and the dial begins to hide the other side of the moon as it becomes a waning crescent moon. Then, the moon-phase disk disappears underneath the dial for the new moon. Finally, the second moon emerges on the other side as a waxing crescent moon, and the cycle continues. Of course, some watchmakers take a different approach.
What Are the Different Types of Moon-phase Watches?
There are different levels of precision when it comes to moon-phase watches. A simple moon phase will be driven by a gear that has 59 teeth (the 29.5-day lunar cycle times two), advancing by one tooth each day. However, the moon’s cycle isn’t exactly 29.5 days; it’s 29 days, 12 hours, 44 minutes, and 3 seconds. Over time, this discrepancy builds up, and the moon phase will need to be adjusted every three years.
To counter this discrepancy, astronomical moon phases use a 135-tooth gear. Astronomical moon phases are typically precise for 122 years until there’s a slight deviation from the moon’s actual position. After 122 years, a watch’s moon phase will need a one-day correction to remain accurate for another 122 years. Some watchmakers have raised the bar with an even more precise moon phase that deviates by one day every 1,028 years.
Another, more complicated, version is the double moon phase, which shows the moon phase in both the northern and southern hemispheres.
Of course, these watches will only remain accurate if you wind them regularly and they run uninterrupted. If the watch loses power and stops keeping time, you’ll need to reset the moon phase. This is one reason why a long power reserve is a good idea on a moon-phase watch. These watches can be fiddly to set using tools, so if you aren’t likely to keep your watch wound, look for one that’s easy to correct using the crown or a pusher.
Arnold & Son Luna Magna
Arnold & Son takes a new approach to moon-phase watches with the Luna Magna watch. Instead of showing the moon phase on an engraved disc, it crafted a three-dimensional moon from marble and aventurine. At 12mm, it’s the largest moon to appear on a watch — hence the name Magna, which means “big” in Latin. To further emphasize the starry night sky, Arnold & Son used its signature small dial off-centered at 12 o’clock, leaving the rest open for aventurine. The moon phase isn’t just beautiful; it is very precise and will remain accurate for 122 years. The back of the watch has a secondary display showing the moon’s age. If you don’t keep the watch wound, it’s easy to reset the moon phase by using the crown. The watch features the A&S1021 caliber, which has a 90-hour power reserve. To accommodate the spherical moon, the front sapphire glass is gently domed. The watch measures nearly 16mm in thickness.
Girard-Perregaux Cat’s Eye Celestial
The Cat’s Eye watch is one of the most iconic women’s watches, instantly recognizable for its unique East-West design. It also has one of the larger moon-phase disks in the industry. Instead of a petite subdial, most of the top half of the dial is taken up by the moon phase, which measures 8.9mm in diameter. The dial and background of the disk are made from shimmering aventurine. The moon-phase disk features stars and planets alongside a magnificent mother-of-pearl moon. Glittering diamond hour markers and accents on the dial evoke more stars. The 18K rose gold case adds warmth to the cool-toned design, and more diamonds encircle the bezel. It features an automatic movement with a 46-hour power reserve.
H. Moser & Cie. Endeavour Perpetual Moon
The creatives at H. Moser & Cie. love to upend traditional ideas of watchmaking in their timepieces and continually strive to raise the bar. It’s not enough for the company to debut its first moon-phase watch — it needed to be exceptional. The Endeavour Perpetual Moon features one of the most precise moon-phase movements in the market. If you keep it wound, it will accurately show the lunar cycle for 1,027 years. Thankfully, it has a seven-day power reserve, so you — and your descendants — have a shot at keeping it wound for a millennium.
The watch showcases H. Moser’s Concept design. The dial is missing many of the signature elements on other watches, including the brand name and hour markers. This lets the beauty of the aventurine dial shine through. A bit counterintuitively, by not having its name emblazoned on the dial, those in the know will instantly recognize it as an H. Moser timepiece. Without any distractions, the pure aventurine dial really evokes an endless night sky. The ultraprecise moon phase is at 6 o’clock. The sleek moon completes the minimalist dial.
Patek Philippe Ref. 5270P
Many perpetual calendar watches include moon phases, but no one does it quite like Patek Philippe. This Grand Complication watch includes a perpetual calendar, a chronograph, and a moon phase. Reference 5270P comes in an elegant platinum case with a unique concave bezel. Both perpetual calendars and chronographs show a wealth of information, typically using many subdials. Including all of this information while ensuring the dial remains legible can be challenging. Patek Philippe chose to display the chronograph time in two subdials, at 3 and 9 o’clock, and combined the date and moon phase in a subdial at 6 o’clock. Two small apertures flank this subdial. The left is a day/night indicator, and the right shows the year in the leap-year cycle. Two apertures in the center of the dial show the day of the week and the month. The watch has a rich green dial with applied hour markers, a railway-style minutes track, and a seconds track.
Rolex is best known for its sporty timepieces, but it also makes the gorgeous Cellini dress watch. It’s the only Rolex watch with a moon phase. The Cellini has classic stylings, including a polished 18K Everose case (the Rolex equivalent of rose gold) with a fluted bezel. The circumference of the white lacquered dial features a wealth of information. There’s a date track, a minute track, and applied hour markers. A long blue hand topped with a crescent moon points to the date. At 6 o’clock, it has a large, shimmering astronomical moon phase crafted from blue enamel. Rolex takes a different approach to display the moon phase. Instead of having the disk with the moon rotate underneath the dial, it shows the new moon with a silver circle and the full moon, which is actually crafted from meteorite, at the same time. A gold arrow at the top of the moon phase shows the position in the lunar cycle.
Hermès Arceau L’Heure de la Lune
You can be sure of two things when Hermès releases a new complicated watch. The French maison approaches complications in a unique way, frequently wowing us with never-before-seen movements, and every watch has a stunning design with a touch of whimsy. The Hermès Arceau L’Heure de la Lune reverses the traditional approach to moon-phase watches that have a rotating lunar disk. Instead, it has two stationary moons representing the moon phase in the northern and southern hemispheres, and two floating dials circle around the moons. One dial shows the time and the other the date.
The extraterrestrial design is in full effect in these watches. The moons are crafted from mother-of-pearl. The northern moon represents the lunar surface, while the southern moon has a pegasus hidden inside of it. Hermès offers traditional dials in materials like aventurine and lapis lazuli, as well as three dials that are literally out of this world. These dials are real meteorites, so you can take a piece of outer space with you wherever you go.
A. Lange & Söhne Richard Lange Perpetual Calendar “Terraluna”
The first thing you might notice about this moon-phase watch from A. Lange & Söhne is that it seems to be missing the moon phase. However, the Richard Lange Perpetual Calendar “Terraluna” displays far more information than a traditional artistic moon phase. It also displays a perpetual calendar on the front in a unique way and the moon phase on the back. The dial has three circles that display the time: one each for the hours, minutes, and seconds. At 12 o’clock, there’s a date aperture. The leap year is shown in a small window at 2 o’clock, the month at 4 o’clock, and the date in a slim cutout at 6 o’clock. The back of the watch displays an orbital moon phase that is so precise that it won’t need to be corrected for 1,058 years. The moon phase shows not only the progression of the lunar cycle but also the position of the moon in relation to the earth.
Chopard Imperiale Moonphase
Chopard uses the shimmering beauty of the aventurine dial to re-create the night sky in the Imperiale Moonphase watch. The dial features five constellations, including the Big Dipper, diamonds representing stars, and a small astronomical moon-phase display. At 6 o’clock, there’s a unique small seconds display. Three carats of diamonds cover the 18K white gold bezel and lugs. This watch features an in-house movement that is a certified chronometer and has a 65-hour power reserve.