The most complex watch made by IWC Schaffhausen is also a personalized astronomical instrument: the back of the watch shows the night sky as you see it from your own home.
ABOUT THE WATCH
Portugieser Sidérale Scafusia
The dial, in the style of a classic Portugieser, features a constant-force tourbillon together with displays for the 96-hour power reserve and sidereal time, which, among other things, is needed to find the same star each night in the same position. The reverse side is a fabulous astronomical module calculated precisely to reflect the owner’s wishes. From a previously defined location, the rotating night-sky disc shows more than 500 stars and constellations with such detail and precision that it would quicken the pulse of any astronomer. Making the necessary allowances for summer time and winter time, the watch also displays the times of sunrise and sunset, sidereal time and a perpetual calendar with the leap years. In view of the enormous amount of work involved and the more than 200 individual configurations possible, only a few watches are produced each year.
Constant-force tourbillon | IWC Schaffhausen
IWC integrated a patented constant-force mechanism into a tourbillon, which ensures that the amplitude of the balance – and thus the watch’s accuracy – remain absolutely constant, initially by disconnecting the escapement from the direct flow of energy generated by the gear train. The energy is stored temporarily in a balance spring and dispensed to the escape wheel. In the process, the tension in the spring is increased once a second and the seconds hand in the tourbillon advances in one-second steps. This ensures an extremely regular and precise rate over a period of at least 48 hours. After approximately 2 days, the mechanism switches from constant-force mode to normal mode, as indicated by the one-fifth-of-a-second movements in the seconds hand.
Features
Case
Movement
Packaging
Sapphire glass, convex, antireflective coating on both sides
Sidereal time
Ecliptic and celestial equator
Sunrise and sunset together with displays for day, night and twilight
Customized celestial chart
Celestial chart showing horizon
Power reserve display
Perpetual Calendar with leap year display and absolute day of the year
Tourbillon with integrated constant-force mechanism
Case
Platinum
Case
Diameter
46.0
mm
Height
17.6
mm
Back case
See-through sapphire glass back
Water resistance
3.0
bar
Calibre
94900
Calibre
Movement type
Manual-winding,
IWC-manufactured movement
