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Inventory no. 37450 - Epact entry

Epact number: 12646

Nocturnal

Unsigned
16th century ?; German ?
Brass; 87mm in length

Main text

This is such a simple instrument, with no date or signature, that even a dating to the 16th century is speculative: it could be from the 17th century.

A volvelle of the reverse side of the nocturnal relates to an alternative way of finding the time at night, but must be used in conjunction with another instrument, namely a sundial where the shadow is cast by the moon. The volvelle then allows an approximate calculation of the solar time.



Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 37,450



Detailed text

The nocturnal side has a date scale on the base plate, with the months indicated by their initials and divided to |1/6|. A volvelle plate rotates above this and is divided into 24 hours, 8 to 12 to 8 being numbered and marked with points, with a long pointer at 12 midnight. half-hours between the numbered hours are marked by arrows. An index arm with a shaped tip pivots on a central, pierced rivet. Shaped and pierced handle.

On the volvelle side the base plate is divided into hours 1 to 12 twice. The moving plate is divided 0 to 30, numbered by 1, with a pointer at 0 / 30.

Jim Ben nett

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