Astrolabe attributed to Gerard Mercator
Record status
Individual type · partial
Period
circa 1570
This gilt brass astrolabe, measuring 316 mm in diameter, is attributed to the workshop of Gerard Mercator and dated circa 1570. The instrument features a circular disc fixed to the limb with 16 rivets, surmounted by a throne with S-shaped brackets.
The rete is engraved with 42 star names or groups and the zodiac circle. It includes seven latitude plates, six of which are calibrated for latitudes between 36 and 60 degrees. A seventh plate serves as a geographical mirror for the Northern and Southern hemispheres. The back of the instrument contains a shadow square and a conversion diagram for equal and planetary hours. An alidade with sighting wings and a rule for declination are also included.
One latitude plate, designed for 43 degrees, is attributed to the Florentine workshop of Giovan Battista Giusti. The instrument is part of the bequest of Robert Dudley to the Grand Duke of Tuscany.
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
- circa 1570
- Type
- German astrolabe
- Maker
- Attributed to Gerard Mercator
- Diameter
- 316 mm
- Material
- Gilt brass
- Latitudes
- 36 to 60 degrees
- Provenance
- Bequest of Robert Dudley to the Grand Duke of Tuscany
- Place recorded
- Germany
- Maker / attribution
- Gerard Mercator (attributed)
Design
- Visible features
- • The limb is engraved with a 24-hour scale marked 1-12 twice. • The rete features pointers for 42 stars or star groups. • The back includes a shadow square and a conversion diagram for equal and planetary hours. • The throne is supported by two ornate S-shaped brackets.
- Back and Inscriptions
- The back of the astrolabe features a shadow square within the lower semicircle. The upper-left quadrant contains a diagram intended for conversions between equal and planetary hours, calculated based on the times of sunrise and sunset, while the right quadrant remains blank. The circumference of the back is marked with scales for degrees, the zodiac, and a calendar. The rule is marked on both arms with scales ranging from 0 to 70 degrees North and 0 to 20 degrees South, labeled respectively as 'Declinatio septent:' and 'Declinatio merid:'.
- Plates and Accessories
- The astrolabe is accompanied by seven plates. Six of these are calibrated for latitudes between 36 and 60 degrees. The seventh plate is a geographical map of the Earth with North and South polar projections, where land masses are gilded and seas are left as bare copper; this specific plate is not fitted with a lug or hole for hanging. One of the latitude plates is designed for 43 degrees, corresponding to Florence.
- Construction and Design
- The astrolabe is constructed primarily from gilt brass and measures 316 mm in diameter. It comprises a circular disc secured to the limb using 16 rivets. The suspension system consists of a throne formed by a bar attached to the limb, which is further supported by two S-shaped brackets decorated with ornamental work. The limb's face is graduated in degrees and divided into four quadrants marked 90 to 10 degrees, alongside a 24-hour scale engraved 1-12 twice. The rete serves as the primary component for star observation, featuring the zodiac circle and 42 named stars or star clusters. The mater is engraved with projections for the latitudes of 90 degrees North and 0 degrees, alongside astrological houses and markings for unequal hours. The instrument includes an alidade, which features a scale labeled 'Horae ortus solis', and sighting wings equipped with a hole and a dot.
Identification
- Inventory number
- 1098
- 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: The instrument is anonymous and only attributed to Mercator based on formal characteristics.
- Research required: The latitude plate for 43 degrees originates from a different workshop, attributed to Giovan Battista Giusti.