3,478.27 years precision in 5 parts.
Dr. Ludwig Oechslin’s moon phase watch displays the moon phase, date, and time. It features a unique moon phase function executed as a 5 part epicyclic gear system that will take 3,478.27 years before its calculation will be off by 1 day. The analogue date display is more readable than a digital display from the same distance, and unlike large digital displays, is not a distraction when checking the time.
The interactive watch below shows how to read the functions, and you can learn about how the function works in the “Mechanics” section. Detailed technical information is available at the bottom of this page. This video of Dr. Oechslin explaining the date spiral for his perpetual calendar is also relevant for his moon phase watch.
Your moon phase watch
ochs und junior manufactures about 50 moon phase watches per year. Each watch is sold directly by cofounder Beat Weinmann from the ochs und junior workshop in Lucerne. You can select your moon phase watch from models designed by ochs und junior in our online store. Or you can design your moon phase watch using our online customizer. With pleasure, Weinmann will guide you to your perfect moon phase watch on the phone, over email, or in person.
The ochs und junior moon phase watch is entirely manufactured in Switzerland. The case, gear system, dial, buckle, and hands are individually-manufactured by Peter Cantieni in Hinwil, Switzerland. Each watch is hand-assembled and regulated by Romana Fux to 0/+5 seconds at the ochs und junior workshop in Lucerne.
A lifetime warranty covers all parts invented by Dr. Oechslin, and the entire watch is covered by a 2 year guarantee. ochs und junior’s small scale and direct sales model allow it to offer uniquely fast and competent service.
The arrows next to the watch above allow you to show different phases of the moon.
The center represents earth and the large dot at 12 o’clock represents the sun. Full moon is when the moon is opposite the sun and earth at 6 o’clock. New moon is when the moon is hidden between the sun and earth at 12 o’clock. The new moon is represented by a dark circle at 6 o’clock.
The 30+1 holes around the perimeter of the dial display the date. The 10 minute markers serve as reference points. For example: the marker indicating 30 minutes also shows the 15th day of the month (30÷2=15). These 5 day markers allow for the date to be read at a glance and after a short time, you can recognize the date intuitively.
The exact minute and second can be read using the date holes, which are spaced at 2 minute intervals. Holes mark even minutes and gaps odd minutes. The holes and gaps are exactly the same width as the minute hand.
How is Oechslin’s moon phase function implemented?
An epicyclic gear train driven by a central finger bonded directly to the hour pipe turns the lunar disk beneath the dial counter-clockwise. The central finger engages with a wheel bearing 12 teeth, whose pinion with 14 teeth meshes with a wheel bearing 18 teeth, whose pinion with 14 teeth meshes with the fixed recessed ring gear with its 109 teeth machined into the underside of the dial (annotated diagram).
What is the benefit of a highly precise moon phase calculation?
The average time between two identical moon phases is 29.530589 days. Most moon phase watches approximate a lunation as 29.5 days, which leads their calculation to be off by 1 day after 2 years. The closer your moon phase calculation comes to the average lunation of 29.530589 days, the “flatter” the difference between your prediction and the actual moon phase. The ochs und junior moon phase calculates the lunation as 29.5306122449 days. As a result, it will predict the moon phase correctly for 3,478.27 years before it is off by 1 day. This means that you only have to set your moon phase one time, and you can trust that its prediction is precise.
42mm x 11mm or 39mm x 11mm (incl. crystal)
42mm titanium: 70g (including sturgeon leather strap and buckle)
42mm sterling silver 925: 109g
39mm titanium: 62g
39mm sterling silver 925: 101g
50m in titanium, 30m in sterling silver 925. Both models are fit for almost any situation in daily life. For swimming, we recommend titanium.
2-part case designed by Ludwig Oechslin. Available in grade 5 titanium or sterling silver 925; additional materials upon request. Visible machining marks. ochs und junior watches require no movement ring due to the extremely small manufacturing tolerances on the case. Available exclusively with a solid case back. Manufacturer: Peter Cantieni / Hinwil / Switzerland.
Moon phase function
5-part epicyclic gear system designed by Ludwig Oechslin. The calculation is precise for 3,478.27 years before it is off by one day. Manufacturer: Peter Cantieni / Hinwil / Switzerland.
30+1 hole date spiral with 5 minute markers that serve as reference points designed by Ludwig Oechslin.
ETA 2824 with 38 hours of power reserve. Hand-regulated by ochs und junior watchmaker Romana Fux to 0/+5 seconds per day. Manufacturer: ETA SA / Grenchen / Switzerland.
Screw-down crown designed by Ludwig Oechslin. Manufacturable on the right or left side of the case. Available in grade 5 titanium or sterling silver 925; other materials upon request. Manufacturer: Pibor SA / Glovelier / Switzerland.
Leather strap: Designed by Ludwig Oechslin for 22mm watch straps with no loops. Visible machining marks. Grade 5 titanium or sterling silver 925; additional materials upon request. The design of the buckle differs slightly for a 42mm and a 39mm case and matches the lugs. Manufacturer: Peter Canieni / Hinwil / Switzerland.
Rubber strap: Classic buckle, designed by Ludwig Oechslin. Visible machining marks. Grade 5 titanium or sterling silver 925; additional materials upon request. The design of the buckle differs slightly for a 42mm and a 39mm case and matches the lugs. Manufacturer: Peter Canieni / Hinwil / Switzerland.
To assure optimal readability of the time at night, we use Super-LumiNova X1. This coating is manufactured by RC TRITEC in Teufen / Switzerland. In principle, all Pantone colors can be made. Super-LumiNova is always applied in conjunction with a color pigment. The brighter the color, the better the luminosity. At night, Super-LumiNova shines green (the option used by ochs und junior) or blue, on special request. The Super-LumiNova coating is applied by hand by ochs und junior watchmaker Romana Fux, or for dials with a color application by Cador in Eimeldingen / Germany and by Monyco in La Chaux-de-Fonds / Switzerland.
Designed by ochs und junior
Watches in the moon phase store are designed by ochs und junior. Individually manufactured, they have the potential to become classics.
Ludwig Oechslin’s rigorously simple designs, the fact that we individually manufacture our parts, and the direct contact we have with our clients enable us to offer the highest possible degree of customization. The customizer shows many possibilities. We are also happy to discuss ideas which are not in the customizer with you. Please contact cofounder Beat Weinmann for a personal consultation.