1815 Moonphase is a luxury watch by A. Lange & Söhne.

On the occasion of the 150th anniversary of Emil Lange in 1999, this watch was presented. The moon phase indication is exactly calculated to deviate only one day of the synodic orbital period in 1000 years - provided that the watch would run continuously and with accurate time setting. Because of this extreme precision, the display is not set exactly on the day, but with the help of an accurate moon age-table on an hourly basis. This small astronomical wonder is accommodated in a movement only 3.85 mm in height and with a diameter of 27.5 mm.

Thus, the solid silver dial of this horological rarity deserves a closer look. Seven golden appliques represent the constellation of the “Big Dipper”. Beneath the central pole star, called Mizar, sits the small Alcor, which was used in the Middle Ages as a test object for good visual acuity. This is an interesting, hid detail that only a privileged circle of owners of the 1815 Moon Phase can observe , beause it is limited to 250 pieces in red gold and 150 pieces in platinum. It was manufactured from 1999 to 2000.