Although known as the astronomical ring, it is principally employed as an ecuatorial solar universal quadrant. Its use was widespread during 18th century.
It is composed of a ring that can be adjusted to various latitudes, a meridian ring showing the latitude scale, a moveable hour ring and a central, grooved bar that is garduated for the months of the year and a perforated cylindeer, which moves over this. It will indicate the solar local time.
Diameter: 100 mm
Thickness: 4 mm