Inventory no. 91897 - Epact entry
Epact number: 64389
Signed 'Hanns Herghamer'
Dated 1492; German
Paper and vellum; 142 mm in diameter
Paper instruments have not survived in great numbers, but this probably does not reflect their currency in the period. In this case the instrument, which is a very simple form of astrolabe, was preserved between the fly-leaf and the cover of a copy of Johannes Angelus, Astrolabium (Augsburg, 1488). The original binding survived and with it the instrument.
Its function is appropriate to the astrological content of the book. It shows the sky divided into the twelve traditional astrological houses, and relates the sun's position in the different houses to the time in equal hours.
Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 91,897
The lower sheet, in vellum, has a circle marked in red with the four cardinal points and divided into equal hours 1 to 12, numbered by 1. There are lines dividing the houses of heaven, numbered 1 to 12. The line for 1, the eastern horizon, is marked '1a dom
A vellum disc, with a painted and decorated centre, rotates at the centre of the circle and has a zodiacal scale with symbols for the signs, each with a 30-degree scale divided to 10, subdivided to 5 with alternate filling, numbered by 10. Alternate signs are marked and graduated in red and brown (black?).
Above the disc is a counterchanged rule, which with the disc is held by a brass pin. The vellum sheet is pasted to a paper sheet with ink writing, on which is the signature 'Hanns Herghamer · 1 · 4 · 9 · 2 ·'.