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 Sky
Moon Tourbillon
Ref. 5002 by Patek Philippe
The rarest complications united in a
wristwatch
On October 5, 2000, Patek
Philippe unveiled the Star Caliber 2000, one of the most complicated
pocket watches of all times. Barely six months later, the Geneva
workshops are introducing a new Grand Complication – now in a
wristwatch format. The “Sky Moon Tourbillon” Ref. 5002 is the most
complicated wristwatch ever built by Patek Philippe, and it is the first
double-faced wristwatch that features a complete presentation of the
nocturnal sky on its reverse side. The new masterpiece displays the
apparent movements of the stars, the orbit of the moon, the moon phases,
as well as the hours and minutes in sidereal time.
A symphony of the most beautiful
complications
As was already the case with
the Star Caliber 2000, Patek Philippe’s goal in the development of the
“Sky Moon Tourbillon” was not so much the number of complications
per se. The real objective was to accommodate the most fascinating
complications in the small case of a wristwatch: a perpetual calendar
with a retrograde date display, a minute repeater, a tourbillon, the
display of sidereal time, and a depiction of the nocturnal sky with the
motion of the stars, the orbit of the moon, and the moon phases. This
turned out to be a formidable challenge because a chart of the heavenly
canopy (as seen in the northern or southern hemisphere) requires a
certain minimum space to demonstrate the movements of the stars in a
sensible and clearly legible manner. The solution adopted by Patek
Philippe was borrowed from the astronomical pocket watches made by the
company: a moving sky chart on the reverse side of the timepiece. The
mechanical module developed by Patek Philippe for the “Star Caliber
2000” was redesigned especially for the “Sky Moon Tourbillon” and
was granted Swiss patent CH 688 171 B5. A minute repeater heralds the
third millennium
The acoustic indication of hours, quarter-hours, and minutes is and
undoubtedly remains one of the most spectacular functions that a
wristwatch can possess. When the slide on the left of the case is
activated, the repeater first strikes the number of hours on a low-tone
gong, followed by the quarter-hours with double strikes on the low-tone
and a higher-tone gong, and finally by the number of minutes which have
elapsed since the last quarter-hour on the higher-tone gong. In the
“Sky Moon Tourbillon”, this chime is implemented in a rare and
fascinating manner. In the comparatively small volume of a wristwatch,
it is extremely difficult to generate a clear and rich-sounding tone. A
few years ago, after intensive collaboration with metallurgists of the
Swiss Federal Institute of Technology in Lausanne, Patek Philippe
succeeded in developing an alloy for gongs that create a particularly
resonant sound. In the meantime, this alloy has been refined, making it
possible to produce a special gong that can be more than one case
circumference long. It is called “cathedral gong” because it renders
the hour strike with a rich, full-bodied tone that like the bells in a
cathedral reverberates for a particularly long period of time.
The tourbillon defies gravity
Every mechanical watch with a balance wheel has a so-called
positional error when held vertically, because the center of gravity of
the balance spring is then outside of its axis of rotation. This error
can be compensated with a tourbillon, a rotating carriage which
incorporates the escapement, balance wheel, and balance spring, and as a
rule turns about its own axis once per minute. Due to this rotary motion,
the center of gravity of the balance spring also rotates about the
balance axis once per minute and thus automatically compensates the
positional error. In the Ref. 5002, the tourbillon, the balance wheel,
and the fourth wheel are located on one axis. This configuration is
particularly difficult to implement, but it best exploits the principle
of the tourbillon. The tourbillon in the Ref. 5002 is quite amazing:
Crafted from steel, the tiny mechanism is composed of no less than 69
individual parts, yet it weighs a scant 0.3 grams – this suggests how
microscopically small and filigreed the individual components must be.
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The perpetual
calendar with a retrograde date
The perpetual calendars of Patek Philippe are legendary. This
also applies to the “Sky Moon Tourbillon”
whose perpetual calendar has been refined with a date display
that has an automatic flyback hand (retrograde date). It
displays the date on a 270° arc on the dial. Every day, the
date hand moves forward by one position and after the end of the
month (the 28th, 29th, 30th, or 31st day) automatically jumps
back to the beginning of the month scale. As opposed to
conventional solutions with cams, this retrograde date is based
on a patented ratchet wheel mechanism that features an extremely
high degree of hand positioning accuracy. At the moment when the
date hand leaps from the end to the beginning of the scale, the
mechanism prevents it from inadvertently rebounding to the
second or third day marker. Thus, when a new monthly cycle
begins, the hand is instantly stopped and reliably retained at
the position of the first day.
The remaining displays of the perpetual calendar are indicated
with four subsidiary dials: the days of the week at 9 o’clock,
the leap year cycle at 12 o’clock, the month at 3 o’clock,
and the moon age at 6 o’clock. All displays are perfectly
harmonized and need not be corrected until the year 2100
provided the watch is regularly wound. 
Heavenly complications on the
reverse side
A very unusual feature for a wristwatch can be seen on the reverse side
of the “Sky Moon Tourbillon”. The canopy of the northern (or on
request of the southern) hemisphere rotates counterclockwise under the
sapphire crystal caseback, showing the motions of the stars and the moon,
the meridian passages of Sirius and the moon as well as the waxing and
waning moon phases. Additionally, two hands from the center indicate
sidereal time on a 24-hour scale. An elliptical contour indicates the
portion of the nocturnal sky which can be viewed from a specific
location. The breathtaking presentation conceals a module with a
patented gear train never before built in this manner.
With its celestial mechanism for the “Sky Moon Tourbillon,” Patek
Philippe has succeeded in achieving an unprecedented degree of precision
in the display of astronomical indications.
A lunar day is defined as the period of time which elapses between two
consecutive passages of the moon across a certain meridian. On average,
it is 24 hours, 50 minutes, and 28.328 seconds long. A lunation (the
period between two consecutive full moons) lasts an average of 29 days,
12 hours, 44 minutes, and 2.82 seconds. A sidereal day is defined as the
period of time between two consecutive passages of a fixed star (Sirius,
for example) across a certain meridian. Its duration averages 23 hours,
56 minutes, and 4.09892 seconds in units of mean solar time. The
geographical longitude of a specific location can be calculated with
sidereal time.
For the respective displays, these deviations from mean solar time
require appropriate transmission ratios in the gear train that delivers
the force from the barrel to the individual astronomical displays. Some
of these ratios favor the accuracy of the moon phase display versus the
sidereal day, others the accuracy of the sidereal day versus the motion
of the moon, etc. Overall, more than 25 trillion possibilities of
varying the reciprocal transmission ratios in the gear train were
computed. From this staggering number, Patek Philippe has found the
optimum variation that achieves the smallest possible error for all
displays. The result of the theoretical calculations has surpassed all
expectations:
• For a lunar day, the error is 0.05 seconds per day, 18.385 seconds
per year, or 30 minutes and 38.5
seconds per century.
• For a sidereal day, the deviation is 0.088 seconds per sidereal day,
32.139 seconds per year or 53
minutes and 33.9 seconds per century.
• For the moon phases, the error is 6.51 seconds per lunation.
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A masterpiece of perfection
The manually wound movement is masterpiece of precision engineering
composed of a total of 686 individual parts, each meticulously finished
by hand. The edges of all steel parts are beveled and each individual
tooth of every single gear is hand polished in an additional process
using a rotating hardwood Continued 3•disk. This degree of perfection
is not an end in itself. Polishing reduces friction at the tooth contact
surfaces, thus contributing significantly to the timekeeping precision
and longevity for which Patek Philippe watches have a legendary
reputation. The plate and the module with the perpetual calendar are
finished on both sides with an engraving technique known as
“perlage” or circular graining. The bridges are decorate with an
engraving technique known as “vagues de Genève” or Geneva striping.
Because of the painstaking processes and work-intensive steps needed to
test timekeeping accuracy, it takes many months to complete one movement.
The result is a flawless marvel of precision engineering worthy of the
prestigious Geneva Seal embossed on its bridge, the highest official
hallmark of quality awarded to mechanical timepieces. Each individual
“Sky Moon Tourbillon” Ref. 5002 watch is delivered with a COSC
chronometer certificate, as are all Patek Philippe tourbillon timepieces.
Perfect technology in a beautiful
case
The case in 18K yellow gold or solid platinum affords both aesthetic
and effective protection of the “Sky Moon Tourbillon” movement. It
looks gracious and elegant despite its sizable dimensions: 42.8
millimeters in diameter and 16.25 millimeters in height. The
comparatively wide case is decorated with an engraving of halved
Calatrava crosses. The crown at 4 o’clock is used to wind the movement
and set the hands on the front side. The crown at 2 o’clock corrects
the position of the sky chart and the hands that indicate sidereal time;
turned in the other direction, it corrects the position of the moon and
the moon phase display. The side of the case also accommodates a number
of correction buttons which are activated with a setting stylus. The
first button, between 11 and 12 o’clock, simultaneously corrects the
date and the day of the week. The second one, between 3 and 4 o’clock,
corrects the month. The third button, between 5 and 6 o’clock,
corrects the moon age display, and the fourth one, between 6 and 7
o’clock, corrects the day of the week only. The slide which starts the
minute repeater is recessed in the case on the left-hand side. The
precious timepiece is worn with a hand-stitched strap made of crocodile
leather; the prong buckle is made of 18K yellow gold or platinum to
match the case.
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The two faces of the Sky Moon
Tourbillon Ref. 5002
The design of the dials on the front and reverse sides of the
timepiece is a challenge in itself. A multitude of indications must be
accommodated on comparatively small surfaces without compromising
legibility and the harmony of the individual displays. The front dial is
crafted from gold with a silvery opaline coating; at its periphery, the
hours are represented by Roman numerals from I to XII. The retrograde
date display is on an inner ring between 2 and 10 o’clock with a
feuille hand made of blued steel. The minutes are indicated on a railway
scale with a gold poire hand that matches the color of the case. The day
of the week and the months are displayed with blued-steel poire hands on
subsidiary dials at 9 and 3 o’clock, respectively. The leap-year cycle
and the moon age are indicated with gold feuille hands on subsidiary
dials at 12 and 6 o’clock. The moon symbols on the moon age display
are made of yellow or white gold to
match the case. The new moon symbol is black. The middle of the dial is
decorated with a pattern composed of small Calatrava crosses.
The rear dial showcases the astronomical functions. It has a 24-hour
scale with Arabic numerals at its outermost periphery, used to indicate
sidereal time with white, balanced poire hands. A blue sapphire crystal
disc with 279 teeth rotates to track the angular motion of the moon and
in a small round aperture shows the moon phases. The sky chart is on a
separate, transparent sapphire crystal disc with 356 teeth. Both discs
are protected by the sapphire crystal caseback which on its inside bears
the 24-hour sidereal dial and a golden ellipse framing the portion of
the sky that is visible from a given location.
A genuine rarity forever and a day
The “Sky Moon Tourbillon” Ref. 5002 is the most complicated
wristwatch in regular production by Patek Philippe. Because of its
complexity and the great amount of time that must be dedicated to the
many highly sophisticated production, assembly, and regulating steps,
annual production is limited to only two watches.
The “Sky Moon Tourbillon” Ref. 5002 is priced at CHF 950,000 for the
18K yellow gold version and CHF 990,000 for the platinum version. The
watches are available exclusively at the Patek Philippe store on the Rue
du Rhône in Geneva.
visit
www.patek.com for more information
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