What Is A Moonphase Watch And How Does A Moonphase Watch Work?

You may have heard of the moonphase complication. However, you may still be wondering – “What is a moonphase watch and how does a moonphase watch work?” Well, that’s what we’ll find out in today’s post.

Personally, I’m a big fan of watches with moonphase complications. I think of it as an artistic interpretation of time. The way the dial shows the true lunar cycle also brings you back to an era when watchmakers started to push the boundaries of complications and movement.

So, without further ado, let’s dive into the wonders of moonphase watches together.

What is a Moonphase Watch? [A Guide to the Moonphase Complication]

A “moon phase” watch is marked by a crescent-shaped aperture. Such a small display on the dial identifies the four intermediate (waxing and waning) phases of the Moon that we can see from the Earth. 

Although there are many names for the changing moon views, watchmakers normally focus on the main four when designing a moonphase watch. These four main phases of the moon are the following:

1. New moon (primary; 0% illumination)
2. First quarter (half moon; 50% illumination; the right side is visible)
3. Full moon (primary; 100% illumination)
4. Last quarter (primary; 50% illumination; the left side is visible) 

Moreover, a standard version of the moonphase complication comprises two moons on a rotating moon disc. The dial displays these moons through a half-circle aperture. Meanwhile, the gap has to hide a part of the moon to show a watch’s exact lunar cycle phase.

History of the Moonphase Complication

Moon Phase display is one of the earliest known complications in watch history. No watch complication is quite as poetic, elegant, and romantic as the moonphase complication.

In terms of functionality, the moon phase’s origin dates back to Ancient Greece. It is believed that they developed the complication to predict astronomical events. And its function remained simplistic for the next hundreds of years.

Although, for wristwatch use, the moonphase complication was first developed in 1925 by Patek Philippe. Since then, the moon phase display has been an eye-catching element that depicts the moon evolving with changes in trends and tastes.

The Moonphase Today

Modern watchmakers continue to create a more accurate version of the moonphase complication. Specific visuals and designs differ from piece to piece. And you’d be blown away by their engineering feats.

Brands like Patek Philippe, A. Lange & Sohne, and H. Moser & Cie are doing something unique. Each watch brand developed a moonphase complication with accuracies of over 1,000 years. Here’s why:

Moonphase accuracy lies in the number of tooth on the watch gear (mainspring barrel). If the moonphase watch has 59 tooth, it has an accuracy of 2.7 years. On the other hand, If it has 135 tooth, that’s 122 years of accuracy. 

Some grand watch complications, including the IWC, have over 500 years of accuracy since their movement has plenty of space.

Specialized watch brands like the Ochs and Junior have created a moonphase complication with up to 3,478 years of accuracy! All of these watches are high-priced by order of magnitude. So, don’t be surprised if these watches are rarely or never seen. 

The creation of these superb moonphase timepieces requires extraordinary talents and ideas. But you can guarantee that the details – from the case to the strap, lugs, and movement – all are brilliantly brought together in one timepiece.

Related: Best Moon Phase Dress Watch

“Bosom” vs. “Radial” Moonphase Watch Complication

There are two types of watches with moonphase complications: the “bosom” moonphase watch and the “radial” moonphase watch.

The bosom moonphase timepiece displays the two twin moons through the aperture. Meanwhile, the radial moon phase watch utilizes a hand to point to the moon’s shape. In this kind of moon phase complication, the indicator hand moves, not the moon’s image.

Most watchmakers prefer to use the bosom moonphase, which showcases their mechanical ingenuity and creativity in presenting the entire lunar cycle.

How long is each phase of the lunar cycle?

The moonphase watch relays the 29.5-day lunar cycle by displaying the current moonphase watch in an aperture on the watch dial. A 59-tooth watch gear that pushes the notch by a mechanical finger daily powers most moonphase watches.

It takes about 29 days, 12 hours, and 44 minutes for the moon to complete one phase cycle. Hence, watchmakers must round up and down in designing the watch movement. Standard accuracy will be off by 0.03 days per month or one full day every two years when they developed the 135-tooth gear.

How accurate are moon phase watches?

Moon phase watches are 99.998% accurate. They will consistently be accurate for 2.5 years. After that, it will have to be manually adjusted. Yet, higher-end moonphase watches are accurate for up to 122.5 years.

Some of the most accurate watches with a moon phase function are from the following brands: A. Lange & Söhne, Patek Philippe, De Bethune, Jaeger-LeCoultre, and Ochs und Junior.

How Do Moon Phase Watches Work?

A typical moon phase watch has two identical moons. A standard 59-tooth gear drives the disc and rotates a complete cycle every 29 and a half days. Therefore, each full moon passes through the aperture on the dial every 29.5 days. The moon appears to wax and wane.

If the moon watch runs solidly for three years, the indicator will lose a day of accuracy. Hence, why do high-end moonphase watches, like from the A. Lange & Söhne and Patek Philippe are developed with a 135-tooth wheel. 

Therefore, these upscale moonphase timepieces need a single manual correctly every 122 years instead of two years in moonphase watches with standard gear.

Moreover, a moonphase watch is one of the market’s most elegant and iconic timepieces. Apart from its style, its exciting history has drawn so much respect from watch enthusiasts worldwide. So much so that various watchmakers developed their signature styles, you’ll instantly know it’s from a particular brand from a few feet away. 

For instance, consider Frederique Constant Manufacture Slimline Moonphase or Omega Speedmaster Professional Moonwatch Moonphase. Both are timeless and make an incredible masculine accessory.

How do you set a moonphase watch?

Since there are different types of moonphase complications, they also have different complexity levels and degrees of accuracy. These differences mean that setting the correct phase of the moon likewise varies.

1. Precaution – The general setting requires you to pull out the crown and move its hands to 6:30. Putting the hands of the watch at the lower half of the dial removes any chance that their position will cause damage to the movement in case you alter the moon disc. 

2. Correct orientation – Based on the assumption that your moonphase watch uses the 29.5-day model, every tooth in gear is equivalent to one day in the lunar cycle. The easiest way to set the moon phase watch is to check the present phase of the moon online.

After checking the phase of the moon, orientate the disc to make the full moon visible. From this point, set the disc again accurately by matching the moonphase displayed online. Lastly, push the crown back, and you’re good to go.

Why are moon phase watches so expensive?

Watches with a moon phase indicator are usually expensive because of their unique designs, intricate movements, precious materials, and other complications. 

Over the years, watchmakers overcame the difference between the actual moon phases and the measured lunar cycle. Also, the movements of the moonphase watches undergo the strictest test of time.

Related: Best Moonphase Watch Under 2000

Clash of the Icons: Top 10 Most Popular Moon phase Watches 

Here are some of the most legendary watches that shine the brightest in the moon phase complication category:

• Orient Star Classic with Moon Phase – This model is among the fanciest moonphase watches worldwide. It is visually playful and indeed a high-end model. Furthermore, it contains Orient’s in-house movement that offers 50 hours of power reserve.

• Baume & Mercier Clifton Automatic Moon-Phase – This watch has an actual moon phase indicator, and an attractive gradient grey lacquered. This timepiece is also designed with solid steel blocks and features a day-date complication and a five-day power reserve. Overall, Baume & Mercier perfected the combination of affordability and class with this watch. 

• Omega Speedmaster Moon Phase – The moon phase disc in Omega Speedmaster is sweet. Since they introduced the moonphase watches from Omega in 1985, they have undergone a significant overhaul. In addition, this model has a radial date sub-dial, a polished hand, and a high-resolution moon phase disc with a photorealistic lunar surface.

• Arnold & Son Luna Magna Moon Phase – Focusing on its moonphase feature, the watch is equipped with a three-dimensional moon indication at 6 o’clock. It’s the biggest rotating moon ever built in a wristwatch. The moon’s appearance is against a starry backdrop, dazzling the timepiece. Moreover, this limited edition watch is also made of an aventurine glass and white marble half sphere. 

• Jaeger LeCoultre Master Calendar Automatic – The moon section in the dial is very well-made. You’ll see the moon phase at 6 o’clock and against the background of a starry midnight sky. Also, this watch gives time and the complete calendar. Overall, this timepiece is very sophisticated.

• Frederique Constant Slimline Moonphase Manufacture – This watch feels solid. It has a pleasant finishing with circular Geneva stripes, a gilded rotor, and blue screws. This model is, in fact, one of the brand’s best-sellers because of its mix of modernity and elegance. 

The case is round and smooth, with nice curves. Also, the proportions of this watch wear better than they look. Each element – the thickness of the bezel, case diameter, length and width of the lugs, width of the strap, size of the crown, and thickness of the case are all coherent with the wrist of the timepiece. 

With Frederique Constant Slimline Moonphase Manufacture, you’ll enjoy the beauty of mechanics at a reasonable price.

• Ball Trainmaster Moon Phase – The moon phase shines through the dial of this watch. It uses various materials and unique little textures to create a fantasy and fun look at the moon and stars. Additionally, it features an automatic caliber BALL RR1801 movement and is water resistant for up to 160 feet or 50 meters. 

Another favorite feature in this timepiece is the 5,000Gs shock resistance and material built to handle even the harshest conditions. Overall, the moon phase is luminous. 

• Christian Van der Klaauw Stella Nebula – While this is a limited timepiece, it’s truly impressive and worth adding to the list of the best moonphase watches. Its overall look breathes craftsmanship.

Christian Van der Klaauw Stella Nebula has a unique component: the ammolite gemstone, which can only be found in Canada. Because of ammolite’s breakable material and rarity, creating this dial has been very complex.

• Christopher Ward C1 Moonglow – This celestial beauty is a great everyday watch. Its moon phase shines with an eternal glow and evokes emotions. I like that the moonphase design is not just an added feature of the dial but the center of attraction itself.

At the center of this watch, you’ll see two lume 3D moons set on a rotating disc with covered stars. Pictures can’t convey the full effect of this timepiece.

• A Lange & Sohne Saxonia Moon Phase 384.026 – Attractive and classy, this moon phase watch features an outsize date and moonphase display. Function-wise, it is precise, with 325 movement parts working together. Lastly, it has three-bar water resistance and 72 hours of power reserve.

Related: Best Moonphase Watch Under $1000

Final Words

People nowadays may not need a moon phase wristwatch to track the lunar cycle since smartphone apps exist for that. However, a moonphase watch works beyond just following the lunar cycle or displaying the wearer’s sense of style. 

Additionally, it exemplifies the creativity and bravado of mechanical watchmaking. If anything, all moonphase watches provide you a link to timekeeping at its most basic – when our ancestors relied on the sky to track the passing of days.

Moonphase watches are not for everyone. But if ever you get hold of one, you know it’s an excellent value for money. Whatever brand you pick, you can guarantee it’s nothing short of a masterpiece.

If you like this review, you might want to read our other reviews at EvesWatch.com.