Electromagnetic radiation at wavelengths between 100 and 380 nanometres is commonly referred to as ultraviolet light. It is not visible as such to the human eye. It penetrates the semi-transparent dial of the GRAND LANGE 1 MOON PHASE “Lumen” and charges the luminous elements, even those that are not yet exposed. The result: the first Lange watch featuring a luminous moon-phase display and a luminous outsize date.

The outsize date consists of a transparent glass units disc with black printed numerals that rotates in front of a luminous background and a tens cross with a white luminous coating and black numerals. Charged by UV light, the display surface of the tens cross also glows even before the date switches. The moon is depicted through two round apertures in the coating of the glass lunar disc, combined with a luminous surface behind it. This timepiece, presented in a limited edition of 200, also features luminous hands and appliques for the time and power-reserve indications.