Total H. 167 cm (66 in.)
Base: 61 × 61 cm (23 ½ in.), H. 105 cm; Diameter of the planetary: 53 cm (19 ¾ in.)
The present extraordinarily precise astronomical sphere belongs to a group of three “sphaera perfecta” created by Jan van den Dam in Amsterdam. Probably an autodidact, he was able to give public lectures in physics and astronomy and to create a very complex astronomical sphere in 1754. He was inspired by another sphere created in 1700 by the clockmaker and instrument maker Steven Tracy. Tracy’s sphere is today housed in the Rijksmuseum, Leiden.
Jan van den Dam named his creation “Sphaera Perfecta” because the small planets imitate the revolution of the real planets with an accuracy of one thousandth which is more extensive than other mechanical spheres.