Display 3: Marine astrolabe
The astrolabe is a flat, circular disk used to represent the movements of celestial bodies. The instrument was already known in antiquity and was described in detail in the 2nd century AD by Claudius Ptolemy in his Almagest.
Sophisticated astrolabes were made, particularly in the Arab, Persian, and later Indian worlds, serving not only to study the starry sky but also to determine time, including for religious purposes.
However, the classical astrolabe proved too fragile and wind-sensitive for use at sea. Therefore, in the 15th century, Portuguese navigators developed a simplified and more robust, but also much heavier, version: the marine astrolabe. This instrument made it possible to measure the altitude of the Pole Star or the sun at sea and thus determine latitude.
During voyages south along the African coast, determining latitude was usually sufficient for navigation. These methods were documented in the 15th century in the first navigation manuals, such as those of Pedro de Medina.
South of the equator, the Pole Star could no longer be used. Navigators had to orient themselves to the sun, or to the much less accurate Southern Cross. For solar observations, tables of solar declination were necessary, which were compiled and distributed in Toledo and Salamanca, among other places.
3.1
Arte del Navigare, 3ste Italian edition, Venice 1609
Maker:
Pedro de Medina, Spain
Collection:
NavigArte
The original first Spanish edition of this book dates from 1545. It is the first and at the same time one of the most important works on maritime navigation. The book was translated several times; this example is the Italian edition of 1609. Pedro de Medina describes here the use of the astrolabe.
3.2
Maghribi Astrolabium, Ca. 1722
Maker:
Anonymous, North Africa
Collection:
NavigArte
A heavy brass astrolabe from the Maghreb, dated ‘1135 AH’ (1722/23 CE). Copy after an original by Isa Ibn Allahdad.
It includes six double-sided planispheric plates for different latitudes, showing the projection of stars onto a flat plane.
3.3
Marine Astolabium from La Rochelle, Ca. 1575
Maker:
Anonymous, Portugal
Collection:
NavigArte
Found in La Rochelle (France). A 3.2 kg bronze astrolabe of Portuguese origin. A marine astrolabe was weighted at the bottom and perforated to reduce wind interference. The instrument was used to determine latitude from the altitude of the midday Sun or the Pole Star.
3.4
Almanach Perpetuum, 1496, Salamanca, facsimile of 1914
Maker:
Abraham Zacuto, Salamanca
Collection:
NavigArte
Once south of the equator, the Pole Star can no longer be used to determine latitude. Only after the annual declination of the Sun became known, and after Zacuto of Salamanca published these declination tables in 1473 (following Toledo), was it possible to use the Sun to determine latitude at sea and to navigate further south beyond the equator
3.5
Amerigo Vespucci , Ioan Stradanus inuent, Ian. Collaert Sculp. Phis Galle Excudit Ca. 1590
Maker:
Jan van der Straet or Johannes Stradanus, Antwerp
Collection:
NavigArte
The print depicts Amerigo Vespucci in a nocturnal setting with an astrolabe and a radiant Southern Cross of four stars. On the table lie a quadrant and a pair of dividers. The men surrounding Vespucci are asleep. In the left portrait Dante Alighieri is shown, with a reference to the Divina Commedia, in which Dante describes the four stars. The verse from the Purgatorio is reproduced in full.
3.6
Sphera volgare novamente tradotta, Printer Bartolomeo Zanetti for Juan Ortega de Carrión 1537
Maker:
Marco Mauro, Venice
Collection:
NavigArte
The first Italian translation of Sacrobosco’s De Sphaera Mundi, with commentary, including descriptions of navigation methods and declination tables, as well as the Southern Cross as a means of indicating the South Pole. This may have been one of the earliest occasions on which these stars were described as a distinct constellation.
3.7
Titlepage Lucas Jansz. Waghenaer 'Le Nouveau Miroir', printed by Belère Antwerp,1600
Maker:
Lucaz Waghenaer, Enkhuizen
Collection:
NavigArte
(On display at the entrance)
This is the title page of the French edition of his famous "Spiegel der Zeevaert" (Mirror of the Sea).
It illustrates the early instruments: the quadrant, the marine astrolabe, the Jacob's staff, the compass, and the sounding lead
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