Patek Philippe Sky Moon Tourbillon Replica: The Two-Dial Grand Complication

Grand Complications Guide • 10 Sections

Most grand complications carry five or six complications. The Patek Philippe Sky Moon Tourbillon carries twelve, in a case built to hold two full dials. That is why it sits in a category of its own.

The double-faced design is what separates the Sky Moon from other grand complications. The front dial carries the time, the perpetual calendar and the moon phase, and the minute repeater strikes from inside the case. Turn the watch over and the back dial shows the sky chart, sidereal time and the moon’s path across the sky. Both dials sit under sapphire crystals and share one movement of 686 components.

Patek introduced the first Sky Moon Tourbillon, the 5002, in 2001. It was the most complicated wristwatch the manufacture had built, and its calibre RTO 27 QR SID LU CL took years of development. Each watch is assembled and adjusted by hand over many months.

Before judging any Sky Moon Tourbillon replica, it helps to know what the original actually does. Here are the 12 complications across its two faces:

Patek has made two main references of the Sky Moon Tourbillon, and they look very different. The 5002 arrived first, in 2001. The 6002G followed in 2013 in white gold, with a hand-engraved case and lugs and an enamel dial, and it is by far the more ornate of the two.

Tip: on Patek’s watch the sky chart on the back turns once every 23 hours and 56 minutes. In photos of a replica, look at how the stars, the Milky Way and the moon are printed, because that is the part you see every day.

When you look at a Patek Philippe Sky Moon replica from the factory side, the reference changes the whole challenge. The 5002 is difficult because of the movement. The 6002G adds the engraving, enamel and surface finishing on top of that.

In replica form the 6002G is the harder of the two because of its engraving. Patek engraves each case by hand; a replica case is engraved by machine. At arm’s length they look similar, while under a loupe the depth of cut and the flow of the scrollwork differ.

From the front, the Sky Moon Tourbillon reads like a classic Patek perpetual calendar, with Roman numerals and the calendar displays arranged around the centre. The tourbillon works inside the movement, where its rotating carriage evens out the effect of gravity on the balance.

The minute repeater is started by a slide on the left side of the case. On Patek’s watch, two hammers strike cathedral gongs of different pitch: the low tone counts the hours, a low-high pair counts the quarters, and the high tone counts the minutes. At 3:47 you hear three low strikes, three double strikes and two high strikes.

The perpetual calendar tracks the date, day, month, moon phase and leap-year cycle. It knows which months have 30 or 31 days, that February has 28, and that it has 29 in a leap year. No manual correction is needed until 2100, when the Gregorian calendar skips a leap year, provided the watch is kept running.

On a replica the front dial is what people see on the wrist, so it carries most of the work: the size and position of the calendar displays and the printing on them. The watch we list under the Sky Moon name is a different design, a single-faced skeleton tourbillon in a rose gold-tone case: through its open dial you see a tourbillon carriage at 6, a moon phase at 3 and a power reserve scale at 9.

Turn the Sky Moon Tourbillon over and the back dial shows a chart of the night sky as seen from Geneva, at 46.2 degrees north. The star disc turns once every 23 hours, 56 minutes and 4 seconds. That is one sidereal day, the time Earth takes to turn once relative to the stars rather than the sun.

Insight: Patek makes very few Sky Moon Tourbillons each year, and each one goes to a client the brand selects.

Around the edge of the celestial disc, sidereal time is displayed in hours and minutes. Sidereal time runs about four minutes a day ahead of the clock on your wall. Over a full year, sidereal time gains exactly one day on solar time. This is because Earth orbits the sun, so after one complete orbit (365 days), the stars have made 366 apparent rotations. Patek built a separate gear train just to track this.

The back dial also shows the moon’s path across the sky, its angular progression, and where it stands relative to the meridian. Few watches carry this display. Patek added it because the back is the astronomical side of the watch, showing what is happening in the sky above Geneva.

The meridian passage indicator shows when the moon crosses the local meridian, the imaginary north-south line directly overhead. It has uses in navigation and tide reckoning, though few owners will ever need it for that.

A replica does not reproduce Patek’s movement, with its 686 parts in a layout that took the manufacture years to develop. What it can reproduce is the outside: the case shape, the dial layout, the hands and the printing.

The minute repeater is the clearest gap. A chiming repeater needs very fine tolerances between hammers and gongs, and gongs tuned to a specific tone, which remains the work of a few specialist workshops. Do not expect a replica of this design to strike the time.

The back dial is the part a replica can render most faithfully, because it is a picture: a dark disc with the stars, the Milky Way and the moon. Check the printing in the photos: the stars should be fine points, and the compass letters and scales clean.

Know these differences before you buy. A replica can give you the look of the Sky Moon Tourbillon; its twelve working complications belong to Patek’s own watch. For how replica movements differ in general, see our replica movement guide.

We do not list the double-faced Sky Moon Tourbillon; the watch under that name in our shop is the single-faced skeleton tourbillon mentioned above. If the star chart is what draws you, the closest watches we carry are the Celestial models: the Celestial 6102P-001 with its dark blue sky-chart dial, the rose gold-tone Celestial 6102R-001 on a black star map and the Celestial 6104R-001 with a stone-set bezel. For a tourbillon under a night-sky dial, there is also the Tourbillon with a starry blue aventurine-style dial. All of them are in our Grand Complications collection.

Here is what each complication does on Patek’s Sky Moon Tourbillon:

Several of these displays exist on very few other watches. Sidereal time needs its own gear train, and the repeater needs gongs tuned by hand, which is part of why the Sky Moon took Patek years to develop.

Few replica makers attempt the Sky Moon at all: the double-faced case is complex, and far fewer people want it than a Nautilus or an Aquanaut. If you look at one, judge it on what the photos show.

Among Patek Philippe designs the Sky Moon sits at the far end of complexity, which is why most replica makers prefer the Nautilus and the Calatrava.

That depends entirely on why you want one.

If you want the Sky Moon for its design, the double-faced idea, the sky chart and the amount of information on two dials, a replica of the design gives you that to look at and wear, along with the size and weight of a large grand complication case.

If you want it as a conversation piece, few watches draw more questions: people pick it up, turn it over and find the sky chart on the back.

If what you want is a chiming repeater and a movement finished to Patek’s standard, only Patek’s own watch delivers that.

The Sky Moon is one of the few grand complications whose appeal is mostly visual: the sky chart and the double-faced case are what people remember. The Grandmaster Chime is the opposite case, since its identity is its sound.

By the ReplicaPatekPhilippe team