Nocturnal and Sundial by Antonius Geminus
Record status
Individual type · partial
Period
1589
This brass nocturnal and altitude sundial, measuring 110 mm in diameter, is signed by Antonius Geminus and dated 1589. The instrument is designed to indicate time by day or night.
The nocturnal side features a base plate with a zodiacal calendar, including constellations, month names in Latin, and day scales. It includes a moving plate with a nocturnal hour scale and a lunar volvelle, as well as a second plate depicting planetary aspects with a lunar phase aperture. An index arm, signed with the maker's name, allows for nocturnal observations. The reverse side functions as an 'organum Ptolemai' form of altitude sundial.
This side includes a latitude scale, a rotating central disc featuring a Rojas-type projection with zodiacal symbols and curved hour lines, and a pivoting alidade. The instrument is equipped with a pierced, decorated handle and a suspension ring.
Evidence at a glance
- Linked sources
- 1
- Photograph views
- 1
- Catalogue references
- 0
Counts describe this entry’s documentation, not authenticity, rarity or completeness. Photographs may show one specimen; check each caption and licence.
Technical characteristics
- Date
- 1589
- Type
- Italian nocturnal and sundial
- Maker
- Antonius Geminus
- Material
- Brass
- Dimensions
- 110 mm diameter
- Place recorded
- Rome
- Maker Signature
- Ants Geminus f: Rom 1589
- Maker / attribution
- Antonius Geminus
Design
- Visible features
- • Signed 'Ants Geminus f: Rom 1589' on the index arm • Pierced and decorated suspension handle • Mediterranean wind names engraved on the rotating plate edge • Includes an aperture for lunar phase indication
- Sundial and Reverse Side
- The reverse side incorporates an altitude sundial known as the 'organum Ptolemai'. This side features a latitude scale ranging from 0 to 90 degrees. A rotating disc is set against this scale, featuring a central Rojas-type projection that displays right ascension lines, zodiac symbols, and curved hour lines for before and after midday. A pivoting alidade and rule are mounted at the center, incorporating a specific scale between the vanes. The edge of this plate is engraved with the names of the eight Mediterranean winds. Additionally, a solar declination scale is present on the edge of the base plate, with graduations arranged in parallel to the equator.
- Provenance and Documentation
- The object is part of the collection at the Museum of the History of Science in Oxford, recorded under inventory number 42143. Its design links to similar instruments produced by Michiel Coignet in Antwerp during the same period, suggesting a connection to broader European traditions of practical mathematics as documented in the writings of Oronce Fine. The instrument acts as a dual-purpose device for calculating time globally. The source notes that its specific design for the altitude sundial matches configurations historically described as a 'horologium generale'.
- Construction and Nocturnal Side
- The nocturnal side of the instrument consists of a base plate inscribed with a zodiacal calendar and month names. The zodiacal scales are divided and subdivided to facilitate precise readings, with the first point of Aries designated at 21 March. A series of moveable plates allows the user to calculate the time and lunar position. One plate provides an hour scale for nocturnal use, while a second plate contains a diagram of planetary aspects and a lunar phase aperture. An index arm featuring an engraved moon and stars facilitates observation, and the piece is finished with a decorated handle and suspension ring.
Identification
- Inventory Number
- 42143
- Source note
- Facts transcribed from the linked source listing or collection record. Attribution and specifications are source-reported and have not been independently authenticated.
Catalogue references
No catalogue numbers recorded. Numbers are only published once transcribed from a verified edition of a standard catalogue — they are never inferred.
Research required
- Research required: Plumb-line for the sundial is missing
- Research required: Solar declination scale usage remains interpretive