Precision in the short and long term
With its eponymous functions, the DATOGRAPH PERPETUAL boasts two sophisticated complications: a chronograph and a perpetual calendar with an outsize date. Hence, it addresses two traditional areas of precision watchmaking that complement each other: short-time measurement and the display of long-term intervals.
The timepiece comes in 750 white gold with a grey dial. Alongside this classic version, a limited special edition is available that distinguishes itself thanks to the exceptional materials used.
Harmony of the displays
Both complex mechanisms interact with precision and are paired with a harmonious dial design that sets the stage for the numerous displays, rendering each one clearly legible. The characteristic Lange outsize date in the framed twin aperture at 12 o’clock marks the tip of an equilateral triangle. The auxiliary dials for the small seconds, day of the week and day/night indicator at 9 o’clock, and for the month and leap-year display as well as the precisely jumping minute counter of the chronograph at 3 o’clock are located below the horizontal centre axis of the dial, forming the base of the triangle.
The harmonious configuration of the indications for time, the calendar and chronograph functions is rounded off with the moon-phase display at 6 o’clock.
The chronograph functions were implemented in typical Lange fashion: a classic column-wheel transmission assures precise and dependable control of all short-time measurements. The precisely jumping minute counter always delivers doubt-free readings of the elapsed minutes while the flyback function makes it possible to stop an ongoing measurement with the actuation of a pusher and to start a new one.
Whereas the chronograph can measure time with an accuracy of one fifth of a second in the here and now, the mechanical precision of the perpetual calendar extends far into the future. The mechanism is programmed to correctly display date, day of week and month across decades while also recognising which years are leap years. Only on the 1st of March 2100, when the leap year is omitted according to the rules of the Gregorian calendar, the calendar display must be corrected by one day.
The moon-phase display also fully lives up to this degree of long-term precision: it will deviate from a true lunation by only one day after 122.6 years if the watch is kept running continuously.
The separate adjustment of the chronograph mechanism and the perpetual calendar already pose quite a challenge, yet the level of difficulty increases immensely when both complications are juxtaposed in one watch and must be harmonised with each other. This feat requires our watchmakers’ utmost technical expertise and artisanal virtuosity.
Movement L952.1
The well-balanced design and artisanal finish of the watch extend into the interior. The reliable manually wound L952.1 calibre comprises 556 individual parts – of which 223 alone make up the calendar mechanism. The meticulously blended composition of different materials and traditional finishing techniques creates a lustrous play of colours ‒ turning the manufacture movement which was assembled twice into a true gem.
A glance through the sapphire-crystal caseback affords mesmerising insights into the chronograph mechanism. It is controlled by a classic column wheel that coordinates all switching sequences. To this end, various rockers and switching levers engage with this wheel. The special dial design necessitates the considerable length of the levers: they ensure that the outsize date mechanism has sufficient space and the lengthier paths to the auxiliary dials that were moved downwards are factored in.
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