Universal Ring Dial
Brass, steel screws
Late 17th century, France
The small suspension ring of this pocket dial slides to different latitudes marked on the large outer ring. As the Sun’s noon altitude changes, the square cursor can also slide in the central bar marked with months. A ray of sunlight passing through a pinhole in the cursor falls on the hours of the equatorial ring.
AMNH Hayden Planetarium Collection 2020