Precession Obsession: Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

I feel like singing, don’t you? How about we sing one of the classics. With a little twist!

Twinkle twinkle little star, though only in terms of relative visible size as many stars would dwarf even our own sun, which itself is actually 109 times the size of the earth.

How I wonder what you are . . . though I have a general idea I still wonder about it; and about the entire universe too.

Up above the world so high, considering the nearest star after our sun is in fact Proxima Centauri, 4.24 light years away. A light year is equivalent to 9 trillion kilometers or 6 trillion miles, so 4.24 light years away is no short trip.

Like a diamond in the sky
, something akin to the largest known diamond in the universe, which was discovered in June 2014 and is actually the center of a white dwarf star weighing in at a whopping million trillion trillion pounds. It’s so new and barely understood it doesn’t even have a name yet.

Twinkle, twinkle little star, how I wonder what you are!

Harmonious stellar inspiration

That song reminds me of some of the famous stars in our sky like the Sun, Sirius, Arcturus, Vega, Betelgeuse, and Polaris – the latter more commonly known as the North Star. The North Star holds some secrets: it’s not one star but in fact five, and the primary yellow supergiant (Polaris A or α UMi Aa) is a variable star, so its amplitude and period of variation change slowly over time.

But the biggest secret is that Polaris hasn’t always been the North Star, and it won’t always be. In fact it will only be our North Star for a couple thousand years or so. Previously, Alpha Draconis (Thuban) was the pole star between the 4th and 2nd millennium BCE, and Beta Ursae Minoris (Kochab) after that from around 1500 BCE to 500 CE. After Polaris we will have Gamma Cephei around a thousand years from now in 3000 CE.

The precession of the earth: over time, earth's

The precession of the earth: over time, earth’s “north” points to different stars as the axis rotates around a circle (aka precession)

The reason for this movement of the stars is due to the phenomenon of precession. Precession refers to the angular change of the rotational axis of a rotating body. Basically, our planet is like a spinning top; its axis slowly rotates as it spins. As it rotates (precesses), the pole and our axis of rotation trace an arc through space of one degree every 72 years, needing approximately 26,000 years for the full cycle.

The precession of a gyroscope: the earth makes a similar movement over a much longer time frame

The precession of a gyroscope: the earth makes a similar movement over a much longer time frame

So while we see Polaris as the North Star for now, your descendents twenty generations down the road from now probably will not. And even though nothing lasts forever, there is something that mimics precession that you can wear on your wrist and pass on to those descendents. And it also happens to proudly profess the words “Jaeger-LeCoultre” on the dial.

Wearable planetary parallel

The watch I am referring to is the illustrious and incredilievable Jaeger-LeCoultre Duomètre Sphérotourbillon Moon, the most recent addition to the already stacked Duomètre collection. Building on the dual-wing platform that underpins these models, the Sphérotourbillon Moon takes a masterpiece and adds more masterful pieces.

And, yes, it is like a model of our planet on the wrist.

Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

But . . . I’ll get to that later. First I want to provide a few good reasons why this stands as one of my favorite JLC pieces. In key words: dual-wing movement; super accurate moon phase; flyback seconds; cylindrical hairspring; bi-axial tourbillon; 42 mm case; dual power reserve; devastatingly beautiful good looks.

Okay, that last one is a bit subjective, I’ll admit. But the rest cannot be denied as serious horological bragging points. I bet most people can’t even name two other cylindrical hairsprings on watches with moon phases, let alone a bi-axial tourbillon. That would be because this watch is in a league of its own.

The dual-wing concept is where it all begins. It’s an extremely effective solution to the problem of chronometric performance versus additional complications. As complications or even unique energy-sapping displays are added, the amount of power available to keep the balance running consistently is reduced. If these complications are running all the time, the negative effects can be counteracted, but in things like a chronograph or with complications that change only at specific times (like a midnight calendar change), the variable power available to the balance will affect the rate that the watch keeps during the operation of those complications or features.

The dual-wing concept takes care of this by utilizing two separate gear trains: one to power the displays and complications and one to power the regulating organ, the bi-axial tourbillon. As a result, the timekeeping is not affected whenever the complications are active, thus assuring complete accuracy of the watch.

View through the display back of the Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

View through the display back of the Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

It’s all in the details

Without all of the other details I mentioned before, the Sphérotourbillon Moon just wouldn’t be the same. There is a dual power reserve so you can keep an eye on the power remaining in both of the barrels, ensuring you always know when the watch needs to be wound.

This is critical for two reasons: for one, making sure the watch stays wound ensures that the accuracy isn’t adversely affected due to power loss; and for another, the Sphérotourbillon Moon happens to house one of the top ten most accurate moon phases existing in a wristwatch.

That moon phase is accurate to one day every 3,887 years. Yeah, you read that right; three millennia from now you’ll still have more than 800 years before you’ll need to worry about adjusting the moon phase ahead the one day it’s going to be off. That dual power reserve helps you keep the watch wound so you won’t need to adjust one of the most precise moon phases you’ll ever see. Thank you, power reserves!

And there is another feature that helps you help it display time accurately too. The flyback seconds, an extremely rare function, allows the tourbillon to continue its motion even while the wearer is setting the hours and minutes, and then allows the user to precisely set the seconds by having the hand fly back to zero at the touch of a button.

This makes for a tourbillon watch that allows accurate-to-the-second setting without adding a hacking mechanism or being required to live with accurate-to-the-minute-ish setting like many tourbillons.

Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

Tourbillon precession, it’s an obsession

The crowning jewel of the Sphérotourbillon Moon, however, is the tourbillon itself. Of course it would be, silly. It’s the crowning jewel because it is a titanium-caged bi-axial tourbillon inclined at 20 degrees with a blued cylindrical hairspring (very difficult to produce) that precesses around a circle every 15 seconds. This thing is a treat to watch, truly. Not only does the cage do a normal 30-second dance of rotation, but the cage also rolls around a second axis like a top ready to fall over.

This action perfectly illustrates the concept of the earth’s precession over 26,000 years, except this happens four times a minute. That is what makes this piece fantastic, incredible horology that also provides a good show. Unless you have an ultra-fast tourbillon, the movement of a typical sixty-second tourbillon can seem sluggish, but not this one.

After the incredible movement mechanics are adequately drooled over, one can also see that the opening for the tourbillon is superb with the stepped, untreated nickel silver plates (of which the entire movement is constructed) and the dial’s eggshell texture is perfect. The layout is breathtakingly, delightfully balanced, which makes this watch pure beauty.

Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

Oh, and like I mentioned before, it’s a most wearable 42 mm (my second favorite size after 40 mm) and only 14 mm thick, making this watch basically jam-packed with goodness in a standard size. It ticks off every single box that a dedicated collector would ask for and a few that the collector didn’t even know he or she wanted.

The Duomètre Sphérotourbillon Moon sits as a pinnacle of Jaeger-LeCoultre engineering, design, and understanding. The only downside for me is the platinum case: I feel that the watch begs for the most noble of metals, stainless steel. But, hey, I’ll chalk that up to another opinion of mine in what could make this watch perfect in its own right.

Maybe that’ll be a future addition to the collection? Who knows, but for now what about a breakdown!

• Wowza Factor * 9.9 A Sphérotourbillon is already enough for a 9 with the rest coming from the design, the moon phase, and just about everything else in this watch!

• Late Night Lust Appeal * 140 g’s » 1,372.931m/s2 A smashing lust appeal for one of my most grailesque of watches. I’m sure you would agree?

• M.G.R. * 71.4 What more can I say that I haven’t already said: Sphérotourbillon, hyper accurate moon phase, dual-wing architecture, and flyback seconds. It’s supertastical!

• Added-Functionitis * Serious Dual power reserve, moon phase accurate to 3,887 years, flyback seconds, 24-.hour indication, and the jewel, the Sphérotourbillon. This calls for a double dose of prescription strength Gotta-HAVE-That cream for this sensational swelling.

• Ouch Outline * 12.3 – Falling Into A Bonfire While Wearing Polyester This is a seriously dangerous ouch, something that nobody wants to have done on purpose. I don’t know if I can admit to being willing to risk it for the piece. But dang if this thing wouldn’t make me think twice…

• Mermaid Moment * Twirly, Twirly, Twirly! It only takes fifteen seconds for a full revolution of the inclined bi-axial tourbillon and about as much time to book a hall and send out invitations to the service!

• Awesome Total * 865 Add the caliber number (389) to the number of components in the movement (476) and this total is a highly worthy Awesome Total!

For more information, please visit

Quick Facts Jaeger-LeCoultre Duomètre Sphérotourbillon Moon
Case: 42 x 14.3 mm, platinum
Movement: manually wound Caliber 389 with dual-wing architecture and bi-axial tourbillon inclined 20 degrees
Functions: hours, minutes, flyback seconds; moon phase, 24-hour display, dual power reserve indications
Limitation: 75 pieces
Price: €225,000

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  8. […] Precession Obsession: Jaeger-LeCoultre Duomètre Sphérotourbillon Moon The watch I am recommendeding to is the renowned as well as incredilievable Jaeger-LeCoultre Duomètre Sphérotourbillon Moon, the most recent addition to the already piled Duomètre collection. Structure on the dual-wing system that underpins these designs, the … Learn more on Quill & Pad […]

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