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Lot Essay
With confidence, this astrolabe can be attributed to Petrus Ab Aggere, a Flemish instrument maker and mathematician who travelled with the court of Felipe II from Brussels to Spain in 1560. This attribution is based on similarities in the general design of the instrument, compared to other signed instruments via several features of style (such as the style of engraving), in the lay-out of the scales and projections as well as construction details.
Petrus Ab Aggere was a mathematician and map engraver who laid the foundation for instrument making in Spain, based on his training in Louvain.[1] He matriculated at Louvain University in 1542 as Petrus Ab Aggere, Bergensis. Other Louvain instrument makers, such as Gerard Mercator, Adrian Zeelst and Gualterus Arsenius also matriculated and it probably meant that they enjoyed certain protection and freedom within the legal network of the university to operate as instrument makers or map engravers.
Only a handful of his instruments have survived; four signed ones and seven attributions, including this astrolabe. He also adapted the large Philips II astrolabe of Gualterus Arsenius of 1566 to the new Gregorian calendar in 1582 (now in the Archaeological Museum, Madrid).[2]
All his instruments testify of an advanced understanding of mathematics and astronomy. Unlike some other Renaissance makers who were more focused on producing a large number of instruments, Ab Aggere seems to have made few instruments but they all feature innovative scales and complicated projections. The latitudes on the plates of his astrolabes refer to places in Spain between 41° and 39° latitude. On this astrolabe: 37° and 40°, roughly corresponding to Sevilla and Cordoba in the South and Toledo, Madrid and El Escorial in the center.
We know of four signed Ab Aggere’s instruments:
1. the earliest one is an equinoctial sundial, now in Chicago, signed Absolvit Bruxelle Petrus ab Aggere in Gratiam D. Francisci de hispania anno salutis Humanae 1558.
2. The second is a simple theodolite, in Florence, signed Absolvit Toleti Petrus ab Aggere Mathematicus Reius [sic.] anno Dni 1560.
3. The third, another equinoctial sundial, in Oxford, of the same style as the first one, but bearing the engraved inscription IN GRATIAM D. PETRI FAG IARDI F.PETRUS AGGERIUS Madrici anno 1562.
The sequence of dates and cities (1558, Brussels; 1560, Toledo; and 1562, Madrid) corresponds to the whereabouts of the Spanish court under Philip II, who in 1556 succeeded his father, Charles V, at Brussels.
The close ties between the Brussels-based court and the emerging Louvain School around 1540 are well known: Mercator made most of his instruments for Charles V and Nicolas de Granvelle. Arsenius, too, made his earlier instruments, up to 1558, for members of the Spanish aristocracy. It appears that Petrus Ab Aggere worked for the Spanish court in Brussels at the latest by 1558. In August 1559, Philip II moved his court to Toledo, from where it subsequently moved to Madrid in 1561. Ab Aggere’s signatures follow this progressive journey faithfully, thereby presenting strong contextual evidence that he formed part of court life as its royal mathematicus. This evidence adds up to an interesting profile of emigration as well as of the traveling of ‘materialized knowledge’ in the person of Ab Aggere.
A fourth signed instrument is a star-shaped polyhedral dial with a monogram P ° A ° F on its basis. Formerly at The Time Museum, it is now in a private collection.[3] This instrument is key in bridging the signed and unsigned instruments. The 12 signs of the zodiac, engraved in the pointers of the stars, form, among others, a liberating clue to attributing the unsigned astrolabes to Petrus Ab Aggere.
On this astrolabe, the delicate strap work of the symmetrical rete is reminiscent of the basic pattern that Mercator initiated around 1545. It became the trademark of the ‘Louvain School’ and was further elaborated by Gualterus Arsenius, Adrian Zeelst and Michael Piquer. Petrus Ab Aggere, too, finds his own personal signature in this pattern and we can associate three other rete’s to this astrolabe:
1. Closest is an astrolabe auctioned by Christie’s in 2018.[4]
2. Florence (Museo Galileo Galilei).[5]
3. Christie’s in 1996.[6]
Typical in all the rete designs is the way in which the strap crosses the ecliptic in the winter; at the start of Sagittarius and the end of Capricorn. This strap mirrors elegantly the arc of the zodiac it crosses. Another strap cuts the ecliptic near the equinoxes at the height of Aries and Libra. This strap, again in all four retes, is partly a straight line creating an architectural ‘framing’ of the overall rete composition. The central Solomon knot of the rete on this astrolabe is very delicate and refined and clearly gives a more balanced and controlled impression than the retes of the two smaller astrolabes that were probably executed earlier.
Two very unusual and sophisticated astrolabes have also been attributed to Petrus Ab Aggere (Madrid MNCT and Chicago, Adler).[7] They were probably made in Madrid around 1580 incorporating important and, for the time and place, unique projections, inspired by Ali ibn Khalaf, instead of the more common Al-Zarqallu that is usually found on the reverse of the Louvain astrolabes. Both astronomers worked in eleventh-century Andalusia, and their designs were included in the Libros del Saber (1277) of King Alfonso X, also called The Wise. His Libros del Saber was a compendium of the then available astronomical knowledge, which was published for the first time in Castilian.
The astrolabe presented here is another proof of Petrus Ab Aggere’s refined craftsmanship and his intellectual pursuits. It further completes the emerging profile of an ‘Hispano-Flemish’ maker, who travelled from Louvain to Madrid to pioneer instrument making in Spain, based on the Louvain tradition, but complemented with advanced Islamic learning from medieval astronomers of Andalusian origin.
[1] K. Van Cleempoel, The Migration of ‘Materialised Knowledge’ from Flanders to Spain in the Person of the Sixteenth-century Flemish Instrument Maker Pertus Ab Aggere, in S. Dupré & C. Lüthy, Silent Messengers: The Circulation of Material Objects of Knowledge in the Early Modern Low Countries, Berlin, LIT Verlag, 2011.
[2] K. Van Cleempoel, El astrolabio de Felipe II, in the exhibition catalogue: Instrumentos cientificos del siglo XVI, La corte española y la escuala de Lovaina, Madrid, 1997, 137-148.
[3] Lot 5 in Sotheby’s, Masterpieces from The Time Museum, New York, December 2, 1999. Harret Wynter Ltd., Arts & Sciences, Scientific Instruments and Curiosities, London, 1983, no. 62.
[4] November 27, 2018, Lot 505: https://www.christies.com/en/lot/lot-6167647
[5] Formerly inv. no. 1108, Istituto e Museo di Storia della Scienza (epact no. 30: https://www.mhs.ox.ac.uk/epact/catalogue.php?ENumber=83160)
[6] S. García Franco, Catálogo crítico de astrolabios existentes en España, Madrid, 1945, n° 20. Christie’s, Fine Scientific Instruments, 13 December, 1996, lot 26.
[7] R. Moreno, D. King and K. Van Cleempoel, ‘A Recently Discovered Sixteenth-Century Spanish Astrolabe’, Annals of Science, 59 (2002), 331-62; for the attribution see K. Van Cleempoel, The Migration of ‘Materialised Knowledge’ from Flanders to Spain in the Person of the Sixteenth-century Flemish Instrument Maker Pertus Ab Aggere, in S. Dupré & C. Lüthy, Silent Messengers: The Circulation of Material Objects of Knowledge in the Early Modern Low Countries, Berlin, LIT Verlag, 2011.
Christie's would like to thank Dr. Koenraad Van Cleempoel, Professor in Art History & Vice Dean, Hasselt University, for his assistance in preparing this catalogue.
Petrus Ab Aggere was a mathematician and map engraver who laid the foundation for instrument making in Spain, based on his training in Louvain.[1] He matriculated at Louvain University in 1542 as Petrus Ab Aggere, Bergensis. Other Louvain instrument makers, such as Gerard Mercator, Adrian Zeelst and Gualterus Arsenius also matriculated and it probably meant that they enjoyed certain protection and freedom within the legal network of the university to operate as instrument makers or map engravers.
Only a handful of his instruments have survived; four signed ones and seven attributions, including this astrolabe. He also adapted the large Philips II astrolabe of Gualterus Arsenius of 1566 to the new Gregorian calendar in 1582 (now in the Archaeological Museum, Madrid).[2]
All his instruments testify of an advanced understanding of mathematics and astronomy. Unlike some other Renaissance makers who were more focused on producing a large number of instruments, Ab Aggere seems to have made few instruments but they all feature innovative scales and complicated projections. The latitudes on the plates of his astrolabes refer to places in Spain between 41° and 39° latitude. On this astrolabe: 37° and 40°, roughly corresponding to Sevilla and Cordoba in the South and Toledo, Madrid and El Escorial in the center.
We know of four signed Ab Aggere’s instruments:
1. the earliest one is an equinoctial sundial, now in Chicago, signed Absolvit Bruxelle Petrus ab Aggere in Gratiam D. Francisci de hispania anno salutis Humanae 1558.
2. The second is a simple theodolite, in Florence, signed Absolvit Toleti Petrus ab Aggere Mathematicus Reius [sic.] anno Dni 1560.
3. The third, another equinoctial sundial, in Oxford, of the same style as the first one, but bearing the engraved inscription IN GRATIAM D. PETRI FAG IARDI F.PETRUS AGGERIUS Madrici anno 1562.
The sequence of dates and cities (1558, Brussels; 1560, Toledo; and 1562, Madrid) corresponds to the whereabouts of the Spanish court under Philip II, who in 1556 succeeded his father, Charles V, at Brussels.
The close ties between the Brussels-based court and the emerging Louvain School around 1540 are well known: Mercator made most of his instruments for Charles V and Nicolas de Granvelle. Arsenius, too, made his earlier instruments, up to 1558, for members of the Spanish aristocracy. It appears that Petrus Ab Aggere worked for the Spanish court in Brussels at the latest by 1558. In August 1559, Philip II moved his court to Toledo, from where it subsequently moved to Madrid in 1561. Ab Aggere’s signatures follow this progressive journey faithfully, thereby presenting strong contextual evidence that he formed part of court life as its royal mathematicus. This evidence adds up to an interesting profile of emigration as well as of the traveling of ‘materialized knowledge’ in the person of Ab Aggere.
A fourth signed instrument is a star-shaped polyhedral dial with a monogram P ° A ° F on its basis. Formerly at The Time Museum, it is now in a private collection.[3] This instrument is key in bridging the signed and unsigned instruments. The 12 signs of the zodiac, engraved in the pointers of the stars, form, among others, a liberating clue to attributing the unsigned astrolabes to Petrus Ab Aggere.
On this astrolabe, the delicate strap work of the symmetrical rete is reminiscent of the basic pattern that Mercator initiated around 1545. It became the trademark of the ‘Louvain School’ and was further elaborated by Gualterus Arsenius, Adrian Zeelst and Michael Piquer. Petrus Ab Aggere, too, finds his own personal signature in this pattern and we can associate three other rete’s to this astrolabe:
1. Closest is an astrolabe auctioned by Christie’s in 2018.[4]
2. Florence (Museo Galileo Galilei).[5]
3. Christie’s in 1996.[6]
Typical in all the rete designs is the way in which the strap crosses the ecliptic in the winter; at the start of Sagittarius and the end of Capricorn. This strap mirrors elegantly the arc of the zodiac it crosses. Another strap cuts the ecliptic near the equinoxes at the height of Aries and Libra. This strap, again in all four retes, is partly a straight line creating an architectural ‘framing’ of the overall rete composition. The central Solomon knot of the rete on this astrolabe is very delicate and refined and clearly gives a more balanced and controlled impression than the retes of the two smaller astrolabes that were probably executed earlier.
Two very unusual and sophisticated astrolabes have also been attributed to Petrus Ab Aggere (Madrid MNCT and Chicago, Adler).[7] They were probably made in Madrid around 1580 incorporating important and, for the time and place, unique projections, inspired by Ali ibn Khalaf, instead of the more common Al-Zarqallu that is usually found on the reverse of the Louvain astrolabes. Both astronomers worked in eleventh-century Andalusia, and their designs were included in the Libros del Saber (1277) of King Alfonso X, also called The Wise. His Libros del Saber was a compendium of the then available astronomical knowledge, which was published for the first time in Castilian.
The astrolabe presented here is another proof of Petrus Ab Aggere’s refined craftsmanship and his intellectual pursuits. It further completes the emerging profile of an ‘Hispano-Flemish’ maker, who travelled from Louvain to Madrid to pioneer instrument making in Spain, based on the Louvain tradition, but complemented with advanced Islamic learning from medieval astronomers of Andalusian origin.
[1] K. Van Cleempoel, The Migration of ‘Materialised Knowledge’ from Flanders to Spain in the Person of the Sixteenth-century Flemish Instrument Maker Pertus Ab Aggere, in S. Dupré & C. Lüthy, Silent Messengers: The Circulation of Material Objects of Knowledge in the Early Modern Low Countries, Berlin, LIT Verlag, 2011.
[2] K. Van Cleempoel, El astrolabio de Felipe II, in the exhibition catalogue: Instrumentos cientificos del siglo XVI, La corte española y la escuala de Lovaina, Madrid, 1997, 137-148.
[3] Lot 5 in Sotheby’s, Masterpieces from The Time Museum, New York, December 2, 1999. Harret Wynter Ltd., Arts & Sciences, Scientific Instruments and Curiosities, London, 1983, no. 62.
[4] November 27, 2018, Lot 505: https://www.christies.com/en/lot/lot-6167647
[5] Formerly inv. no. 1108, Istituto e Museo di Storia della Scienza (epact no. 30: https://www.mhs.ox.ac.uk/epact/catalogue.php?ENumber=83160)
[6] S. García Franco, Catálogo crítico de astrolabios existentes en España, Madrid, 1945, n° 20. Christie’s, Fine Scientific Instruments, 13 December, 1996, lot 26.
[7] R. Moreno, D. King and K. Van Cleempoel, ‘A Recently Discovered Sixteenth-Century Spanish Astrolabe’, Annals of Science, 59 (2002), 331-62; for the attribution see K. Van Cleempoel, The Migration of ‘Materialised Knowledge’ from Flanders to Spain in the Person of the Sixteenth-century Flemish Instrument Maker Pertus Ab Aggere, in S. Dupré & C. Lüthy, Silent Messengers: The Circulation of Material Objects of Knowledge in the Early Modern Low Countries, Berlin, LIT Verlag, 2011.
Christie's would like to thank Dr. Koenraad Van Cleempoel, Professor in Art History & Vice Dean, Hasselt University, for his assistance in preparing this catalogue.