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Mariner's astrolabe by Francisco de Goes, Portugal, 1608 — view 1 of 1
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Instruments · Mariner's astrolabe

Mariner's astrolabe by Francisco de Goes, Portugal, 1608

DocumentedDocumented from the holding institution's catalogue record.
Maker / attribution
Francisco de Goes (maker)
Date
1608
Country of origin
Portugal
Place
Portuguese
Object type
Mariner's astrolabe
Materials / technique
bronze
Dimensions
diameter 197 mm
Holding institution
Museo Galileo, Florence
Accession / object no.
Inv. 1119
Credit line
Museo Galileo, Florence
Catalogue title (original)
Mariner's astrolabe (English)

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Record summary

Held and catalogued by Museo Galileo, Florence (object number Inv. 1119), this is a mariner's astrolabe by Francisco de Goes, made in Portuguese, Portugal, dated 1608. The Atlas places it in the Early Modern Horology period (1600 – 1750) of its Instruments collection. Materials and techniques recorded by the source: bronze. Recorded dimensions: diameter 197 mm. The record is illustrated with 1 photograph.

Assembled from the source record's structured fields. Dates and attributions are given as the source states them; where a field is missing the Atlas leaves it blank rather than estimating.

Catalogue description

Catalogue description — Museo Galileo

This mariner's astrolabe, made by Francisco de Goes, is fitted with a suspension ring, a degree scale (only half of which has been engraved), and an alidade. On the alidade are mounted two large square plates, one of which is perforated. The instrument served to measure the altitude of the Sun, which was indicated by the alidade on the degree scale when a ray passed through the front hole and struck the center of the back plate. Provenance: Robert Dudley bequest to the Medici collections.

Provenance

Medici collections

Historical context

Early Modern Horology (1600 – 1750)

Huygens' pendulum and balance spring transform accuracy; English makers develop the anchor and deadbeat escapements.

Pocket sundials, Butterfield dials and sandglasses remained essential companions to imperfect clocks; navigators used sandglasses and the log line; observatories began to combine telescopes with pendulum clocks.

Read the period in the timelineMore instruments from this periodEarlier: Renaissance Horology

Atlas type guide

Astrolabes, quadrants and astronomical compendia

The planispheric astrolabe is a two-dimensional model of the sky. A pierced rotating star map (the rete) turns over a plate engraved for a particular latitude; by aligning a star or the sun with its observed altitude, the user can read the time of day or night, the time of sunrise and sunset, and solve many other astronomical problems. Developed in the Hellenistic world and refined by astronomers in the Islamic world from the eighth century, it reached Latin Europe through al-Andalus.

Quadrants, compendia, armillary spheres and later orreries belong to the same family of instruments that model the heavens. They were teaching tools, status objects and practical time-finders. Many surviving examples are signed and dated, which makes them important evidence for the history of instrument-making workshops in Baghdad, Isfahan, Lahore, Toledo, Louvain, Nuremberg, London and elsewhere.

What to look for

  • The latitudes engraved on the plates — they show which cities the instrument was made for.
  • The script and calendar used: Arabic or Persian inscriptions, abjad numerals, Hebrew or Latin text indicate tradition and region.
  • The design of the rete: the number of named stars and the style of the star pointers changes by region and period.
  • Shadow squares, unequal-hour lines and zodiac scales on the back (dorsum).
  • Signatures, dedications and dates, often hidden on the throne (kursi) or the back.

Dating clues

  • Signed and dated astrolabes allow precise dating; undated ones are attributed by star positions on the rete, which shift slowly through precession.
  • Gothic-style retes with tracery are typical of European instruments of the fourteenth and fifteenth centuries.
  • Printed paper astrolabes and planispheres became common from the sixteenth century onward.

General guidance written by the Atlas editors about this kind of object. It is not a statement about this particular piece; for that, rely on the source record above and on physical examination.

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