Roemer's Jovilabe

Constructed by Ole Rømer in the year of 1677. 

Artisan unknown. 

The original machine was destroyed during the fire of Copenhagen in 1728. 

This reconstuction is based on an original copperplate by Rømer. 

The Jovilabe is a model of Jupiter and its four large moons symbolised by pearls. From a peephole in the cabinet, the moons can be observed as seen from the revolving Earth. The angle between Jupiter and the Earth is adjustable. A small gear reproduces the revolutions of the four moons. When the calculator is turned, the time dials can be seen one dial for the hours of the different days of the week, and another dial for 26 weeks of a year. 

The length of the reconstructed machine is 324 millimetres (one royals French foot), its width is 135 millimetres and the height is 153 millimetres. The machine weighs approximately 1,5 kilos. 

About Roemer's discovery