Introducing The New Patek Philippe Sky-Moon Tourbillon At 'Rare Handcrafts' Geneva

The new version of the Sky-Moon Tourbillon remains technically the same as the outgoing model. The watch has displays on both the front and back (which means you forego the pleasure of any view of the movement, although you certainly get something back in terms of information). Topside are the perpetual calendar indications, including day, date, and retrograde month displays, along with mean civil time, and a moonphase; there's also an indication showing where you are in the Leap Year cycle.

The back of the watch shows the astronomical complications (although strictly speaking, you can think of the perpetual calendar as an astronomical complication, as it reconciles the Gregorian calendar with the length of an actual year).

On the back, there's a display of the night sky as seen from the Northern Hemisphere (I've always wondered whether, for the well-heeled client south of the Equator, it's possible to order a Southern Hemisphere variant – where there's a will, there's a way). The portion of the sky visible above the horizon is the part inside the oval, with the points of the compass shown as well, in order to orient you. The orbit and phase of the Moon are also displayed. The two hands show sidereal time, or "star time."

Sidereal time indications are fairly rare as they are of no practical use unless you happen to be an astronomer, but they pose an interesting challenge to the watchmaker, who has to calculate separate going trains for mean civil time and for sidereal time. A day is usually defined as the amount of time it takes for the Sun to return to a given point in the sky. Depending on the time of year, the length of a true solar day can vary from the time shown on a clock by up to fifteen minutes (this is the so-called Equation Of Time) and by convention, we give the day a mean, or average, length of 24 hours. The mean local solar day is then used as the basis for civil time, which is the time in use at all locations in a given time zone.

Sidereal time, on the other hand, is based on the amount of time it takes for a given star to return to the same point in the sky. You might think it would be the same as a solar day. However, as the Earth rotates, it's also moving along its orbit at the same time. The Sun is close enough that the Earth actually has to rotate slightly more than one full rotation to bring it back to (say) its zenith. The stars, however, are far enough away that the effect is negligible, and so a sidereal day is slightly shorter than a solar day, by about four minutes.

Rounding out the complications is the minute repeater, which is activated in the traditional way, by a slide in the side of the case.

The previous version of the Sky Moon Tourbillon was in white gold – the new model is in rose gold but it largely duplicates the engraving motifs of the discontinued model. In addition to the engraving, a couple of different enameling techniques are used as well. The dial periphery and moonphase aperture, as well as the moonphase disk, are done in a technique called champlevé, in which metal is hollowed out and then filled with enamel before firing. The inner part of the dial is decorated with cloisonné enamel – this technique involves shaping flat gold wire into various forms and then filling the resulting cells with enamel.

The engraving remains as elaborately baroque in the new Sky Moon Tourbillon as in the outgoing model – even the hands get the engraver's attention (Patek says it takes about 100 hours to execute the engraving, which I have no reason to doubt). The complex articulation of every surface looks even more pronounced in the new model, probably thanks to the degree to which red gold emphasizes case details and geometry in comparison to white gold.

Although the Sky-Moon Tourbillon 6002R-001 is debuting at the Rare Handcrafts Exhibition (which is being held in Geneva at Patek's HQ, from June 16th to 26th), this is not a unique piece, but a regular production model. As with all of Patek's high complications and high craft pieces, this is an application piece, price on request. I cannot emphasize enough, however, the degree to which you would be unrealistic in the extreme to expect change back from a million CHF.

You can, however, expect to get a nifty set of cufflinks in thanks for your patronage.

The Sky-Moon Tourbillon, after twenty years, remains one of the most unapologetically go-to-hell watches in the world. In complexity and craft, it is one of a small handful of watches that are remarkable in themselves, but also functional museums of ultra-high-end Genevan horology. Sure it ain't cheap (to put it mildly) but you get more horological content in one watch than most brands have in their entire catalogue. The aesthetics are not for everyone – living with a watch like this is probably something like living with the Farnese Table in your breakfast nook. But if you have the scratch, the interest, and the inclination, this is about as big as horological big guns get.

The Patek Philippe Sky-Moon Tourbillon, ref. 6002R-001: case, red gold, engraved to within an inch of its life, 44mm x 17.35mm (which ain't half bad considering its complexity) "not waterproof, humidity and dust protected only." Movement, the Patek Philippe caliber Caliber R TO 27 QR SID LU CL.

Front side: Perpetual calendar with retrograde date hand. Hours and minutes of mean solar time. Day, month, leap year in apertures. Moon phases. Reverse side: sidereal time, sky chart, phases and orbit of the moon. One minute tourbillon with minute repeater. 38mm x 12.61mm, which is still amazingly flat, all things considered, even after 20 years. 705 parts under 24 bridges, running at 21,600 vph in 55 jewels. Gape at it in dumbstruck awe at Patek.com.