Planetarium of Christiaan Huygens, The Hague, 1682
Inv V09997

In 1682 the Hague instrument-maker Johannes van Ceulen completed this unique planetarium, designed by Christiaan Huygens. It was intended for the celebrated Académie Royale des Sciences in Paris, but because of the premature death of its powerful patron Jean-Baptiste Colbert it was retained for the Netherlands.The planetarium shows to scale the orbits and positions of the various planets around the sun. Various technical tours de force illustrate Huygens' genius. For example, all the planets are propelled by one diagonal axle. For the calculation of the ratio of the cogwheels he used a new mathematical gimmick devised by himself: the chain fraction development. He was able approximate the orbits of the planets in eccentric circles. A spiral spring with a balance wheel provides the drive. Yes ... that was also an invention of Huygens'.