Hemisferium Hanging Astronomical Ring Dial PendantThe Astronomical Ring Dial is a replica modelled from an early instrument created by Dutch mathematician and cartographer, Reiner Gemma Frisius, in the 16th Century. It was used by scientists and navigators to make astronomic measurements and determine the time during the day or at night. Several different kinds of astronomic dials existed, and the larger ones could indicate the time to the minute and for a long time were the only way to know if