bavarikon4UDescription
This nocturnal of the Deutsches Museum is made of ivory and wood. Time can be measured with it at night by determining the angle between a star and the North Star. In principle, the nocturnal is a representation of the apparent movement during 24 hours of the rear wheels of the Great Bear (Ursa Major) and Little Bear (Ursa Minor) constellations around the North Star (Polaris) in the centre.
The instrument is made of three discs that can be adjusted. On the lower disc, the months are indicated by days (1-28/31) and zodiac symbols. On the upper rotating disc, the age of the moon (1-30) can be set. Above it, there is a small disc, to which the pointer arm is attached. To use the instrument, one should hold it like a hand mirror by the ivory handle.
An ivory inlay of the arm bears the engraving "BOTH-BEARS", which means that either the Big Bear constellation or the Little Bear constellation can be used for the correct angular adjustment of the firmament. The North Star is sighted through the hole in the centre of the instrument, after the discs are preset. If the fingers of the index hands, inscribed "LB" (for Little Bear) and "GB" (for Great Bear), point to certain stars in the respective constellation, the instrument is correctly aligned. In that case, the hour scale on its back shows the right time.
Author
Mareike Wöhler 2018