Although it is known as the Astronomical Ring (Annulus Astronomicus), the full name of this instrument used for telling solar time and other astronomical measurements is the Universal Equinoctial Ring. Its principle is that of the Universal Equatorial Solar Quadrant.

There were several types of astronomical rings, the larger ones could tell the time to the minute and were for a long time the only way to know if mechanical clocks were working properly, without having to resort to an astronomical observatory. In this smaller version the Latitude is fixed (40,4º). (H 90).

Measurements:

Diameter: 45mm / Thickness: 4mm