THE FUNCTIONAL PRINCIPLE OF THE MOON-PHASE DISPLAY.
Lange’s lunar disc is continuously driven by the hour wheel. An intricate transmission with four different gear ratios assures that one revolution corresponds to the synodic lunation of about 29.531 days with an accuracy of 99.998 per cent. As a result, the display will deviate from the actual position of the moon by just one day every122,6 years.
In simpler movements with lunar discs driven by 59-tooth wheels – which round the orbit of the moon down to 29.5 days – this unavoid-able deviation occurs in just 30 months.
ANIMATION OF THE MOON-PHASE MECHANISM (MOV 1.0 MB)
