Geographical Astrolabe
Record status
Individual type · partial
Period
Late 16th century ?
This gilt brass geographical astrolabe, measuring 108 mm in diameter, features a projection of the geographical sphere from the North Pole to the Tropic of Capricorn rather than the standard celestial sphere.
Attributed to the late 16th century and signed 'ARN', the instrument consists of a mater with a pierced throne, a limb with an hour scale, and a rotating plate engraved with a terrestrial map. The map displays continents, oceans, and specific locations such as Peru and Java, alongside a monogram and the motto '?SIC ? VITA ? PER ? HORAS'. The back includes a degree scale, a zodiacal scale, an eccentric calendar, an unequal hour diagram, and a double shadow square, with an integrated lunar volvelle and aspectarium.
The museum notes that the presence of errors in spelling, unusual scale divisions, and the absence of a rete suggest its authenticity is questionable.
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
- Late 16th century ?
- Type
- French astrolabe
- Maker
- ARN
- Origin
- French
- Diameter
- 108 mm
- Material
- Gilt brass
- Condition
- Missing components
- Place recorded
- France
- Maker / attribution
- ARN
Design
- Visible features
- • Signed with monogram 'ARN' • Terrestrial map covering North Pole to Tropic of Capricorn • Lacks the original rete • Includes a double shadow square on the back
- Scales and Functions
- The reverse of the astrolabe is highly complex, featuring an outermost degree scale and a zodiacal scale with symbols and names. The calendar scale is described as eccentric and is marked 'CERCLES EXENTRIQVE', while the degree scales are marked 'CERCLES CONCENTRIQVE'. Additional features include an unequal hour diagram in two quadrants, a perpetual calendar, a lunar volvelle, and an aspectarium positioned in the central circle. The lower section of the reverse contains a double shadow square with scales divided to 3, alongside images of stars and a profile of the moon. Modern components include the screw, nut, alidade, and index.
- Construction and Design
- The instrument is constructed from gilt brass and measures 108 mm in diameter. It comprises a mater with a thin sheet of brass, a soldered, pierced throne, and an attached limb. The limb features an hour scale ranging from 0 to XII twice, rendered in Roman numerals, and includes subdivisions of 20 and 4 minutes. The instrument incorporates a rotating plate engraved on one side with a terrestrial map, mapping the world from the North Pole to the Tropic of Capricorn. The design includes the names of various oceans and continents, including labels for Peru and Java, and incorporates figures alongside the monogram 'ARN' and a motto. The rete is missing.
- Authenticity and Condition
- The holding museum reports that the instrument contains several inconsistencies. Specifically, there are identified mistakes in the spellings of text on the instrument, and the scale divisions are described as odd. These internal discrepancies, combined with the presence of unusual markings, lead the museum to state that the authenticity of the object is doubtful. The instrument is documented in historical literature, specifically in the second volume of R. T. Gunther's 'The Astrolabes of the World'.
Identification
- Inventory number
- 44359
- 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: Authenticity is described as doubtful due to orthographic errors and scale irregularities
- Research required: Date is recorded as late 16th century with a question mark