МАЭ № 7717-5. МЛ-456

Diptych sundial

late 16th - first half of the 17th c.

elephant ivory, metal, glass beads (?), paint, thread

32-rhumb ring scale (from the East right-side hour-hand) with alidade-pointer. Ring-shape through opening to use the compass when folded. In work (open) position, in the upper part, - vertical altitudinal dial with "pin" gnomon (with scale representing family of hyperboles, marked by Zodiac symbols), functioning as rough calendar. Lower is vertical dial with thread gnomon for latitude about 48°,5. Scale VII-ХII-V with points in 1/4 hour. Compass box - hollow in the 2nd plate. Scale of horizontal dial with thread gnomon for latitude 48°,5, scale VII-ХII-V with points in 1/4 hour is around the compass. On the unused part of the plate is horizontal dial with "pin" gnomon 10-23 (red figures) in the "Babylion" and 2-14 (black figures) in "Italian" system of time computation. 2 plates are on the reverse side - sidereal clock (nocturnal), 29,5-day lunar calendar and table of epacts for each year of one of 19-year cycles of Julian and Grigorian calendars.

History of Science Monuments. 14th-19th centuries. Mikhail Lomonosov Museum