A. Lange & Söhne caliber L096.1
The orbital moon-phase display consists of the celestial disc decorated with countless stars, the lunar disc, which lies beneath it, and the earth disc in the centre. The balance occupies the position of the sun. The moon can be seen through a round aperture in the celestial disc.
In slightly more than 29.5 days, the moon orbits the earth once – in an anti-clockwise direction. A planetary wheel train assures that the moon phase is always correctly displayed. The mechanism is engineered to such a high degree of accuracy that it takes 1058 years before a correction by one day is required.
In the middle of the celestial disc, the earth disc rotates through 360 degrees once a day. It is daytime on the half that faces the sun (the balance) and night-time on the other. The peripheral 24-hour scale provides a rough time-of-day reference for regions in the northern hemisphere.
A constant-force escapement inside the calibre L096.1 movement controls the delivery of the enormous amount of energy stored in the twin mainspring barrel to assure a consistently high rate of accuracy across the entire 14-day power reserve period. In ten-second intervals, this mechanism releases a consistently identical portion of the available energy to the balance, thus assuring that the torque remains constant. At the 6-o’clock position on the dial, a power-reserve indicator in the form of a circumferential ring tells the owner when the time has come to provide the movement with fresh energy via the winding crown.