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Lot Essay
The instruments of the two prolific astrolabists Abû Bakr ibn Yûsuf, who flourished in Marrakesh ca.1200, and Muhammad ibn Fattûh al-Khamâ'irî, who flourished in Seville about the same time, with their very different distinctive designs and, in both cases, brilliant workmanship, provided the inspiration for a succession of artisans in both the Maghrib and al-Andalus, working in either one or the other tradition. (For one of al-Khamâ'irî's astrolabes see Gunther, Astrolabes of the World, no. 130, and for the Strasbourg astrolabe of Abû Bakr ibn Yûsuf see ibid., no. 124, or preferably, Debauvais & Befort, Astrolabes de Strasbourg, pp. 59-121. See also King, In Synchrony with the Heavens, figs. X-4.3.2, 4.3.3 and 4.7.2. For a list of surviving Andalusi and Maghribi instruments after ca.1200 see ibid., XVIII-1.6 and 2.4. On astronomy and instrumentation in al-Andalus and the Maghrib see Vernet & Samss, eds., El legado científico andalusí, and King, "Astronomy in the Maghrib", respectively.)
In particular, the astrolabes of al-Khamâ'irî were often imitated, but unlike the works of the master, the 20-odd copies are all unsigned and undated. Also, it is not obvious whether they were made in al-Andalus (that part of the Iberian peninsular still in Muslim hands at a given time) or in the Maghrib. Nevertheless, they maintain the excellence of al-Khamâ'irî's astrolabes and their intricate workmanship. On the other hand, since all these instruments are engraved in an elegant Maghribi kûfî script, which barely changed over the centuries, these unsigned instruments are extremely difficult to date. In general, the more careful the engraving, the older the piece. However, most unsigned Maghribi or Andalusi astrolabes of this type have not yet been studied in detail, so that we have no proper guidelines for researching a single piece.
In the case of the present composite astrolabe, we can identify four plates that can be dated ca.1200 and attributed to Abû Bakr ibn Yûsuf, and two plates that must be considerably later. Whilst the markings inside the main frame or mater at first sight could be dated ca.1200, the date of the equinox on the back suggests a later date of ca.1700. Alas, the instrument does not speak. It has not been professionally examined and a detailed description based on photographs must suffice here.
The distinctive throne consists of two waved bars facing each other and "standing" on the rim. It is partly covered with a "pair of shoulders" to which a shackle is attached. The basic design is that of Abû Bakr ibn Yûsuf, but the curious cover is of a kind not attested elsewhere and possibly served only to reinforce the frames underneath, which may be broken.
The limbus is divided and labelled for each 5°, with subdivisions for each 1°. The mater is densely engraved with standard astrological information arranged in a series of rings. For each sign of the ecliptic, the limits according to "the Egyptians" and according to Ptolemy, the lords, faces and triplicities, are given, using the last letter of the names of the planets as abbreviations. (On astrological information on astrolabes see King, In Synchrony with the Heavens, X-4.6, and the references there cited.) The markings are identical to those on various astrolabes of Abû Bakr ibn Yûsuf, notably his 1208 Strasbourg piece (on which see Debauvais & Befort, Astrolabes de Strasbourg, pp. 66-67). One does not expect this quality of engraving on a Maghribi astrolabe from ca.1700 (see below); rather, it approaches the same quality as the engraving of Abû Bakr.
The rete is typical of the school of al-Khamâ'irî (which is quite different from the retes of Abû Bakr), and indeed resembles that on his Oxford astrolabe (Gunther, no. 130). The horizontal bar is counter-changed on both sides at the ecliptic and inside the ecliptic. The lower equinoctial arc is also counter-changed twice. There is a trace of a circular frame beneath that frame. The star Regulus, whose pointer serves as a support for the lower eqinoctial arc, is placed at ca.Leo 26°, enabling us to date the rete to ca.1700. Each of the pointers bears a silver stud, in the tradition of both al-Khamâ'irî and Abû Bakr, and their predecessors in 10th and 11th-century al-Andalus and the Maghrib. There are also four silver studs on each radial axis for rotating the rete. The 6+7+6+7 = 26 stars are typical of the Western Islamic astrolabe tradition. They are as follows, arranged in the four quadrants starting at the vernal equinox on the left hand side:
batn qaytûs - \kz\K Cephei; ra's al-ghûl - \kb\K Persei; al-dabarân - \ka\K Tauri; 'ayyûq - \ka\K Aurigae; qadam al-jawzâ' - \kb\K Orionis; mankib al-jawzâ' - \ka\K Orionis / al-'abûr - \ka\K Canis Maioris; al-ghumaysâ' - \ka\K Canis Minoris; yad al-dubb - \ki\K Ursae Maioris; shujâ' - \ka\K Hydrae; rijl al-dubb - ? Ursae Maioris; qalb al-asad - \ka\K Leonis; al-ghurâb - \kg\K Corvi / al-a'zal - \ka\K Virginis; al-râmih - \ka\K Bootes; fakka - \ka\K Coronae borealis; al-hayya - \ka\K Serpentis; qalb al-'aqrab - \ka\K Scorpionis; al-hawwâ' - \ka\K Ophiuchi / wâqi' - \ka\K Lyrae; al-tâ'ir - \ka\K Aquilae; al-dulfnn - \ke\K Delphini; dhanab al-jady - \kd\K Capricorni; ridf - \ka\K Cygni; mankib al-faras - \kb\K Pegasi; dhanab qaytûs - \ki\K Ceti
Four plates bear altitude circles for each 2° labelled for each 6°, and azimuth circles above the horizon labelled for each 5°. There are special markings for nightfall (shafaq), midday (khatt al-zawâl), the prayers shortly after midday and during the afternoon (al-zuhr and al-'asr), and daybreak (fajr), and the altitude circles for argument 18° above the horizon are also marked for daybreak and nightfall. The seasonal hours below the horizon are labelled with the appropriate ordinals. The organization of the arguments for the various markings is typical of Abû Bakr ibn Yûsuf; indeed, the plates were without any doubt engraved by him. On each plate there is an inscription: for the latitude of * and all localities whose latitude is *, with maximum length of daylight * (hours and) * (minutes)". The following localities are featured:
1a - Sijilmasa - 29° - 13h 13m; 2a - Marrakesh - 31° - 14h 3m; 1b - Jerusalem - 32° - 14h 8m; 2b - Fez - 33°40' - 14h 17m; 3a - Ceuta - 35°20' - 14h 27m; 3b - Almeria - 36°30' - 14h 33m; 4a - Toledo - 40° - 14h 54m; 4b - Saragossa - 41°30' - 15h 4m
The values for maximum daylight are accurately computed for a value of the obliquity of the ecliptic of 23°51', which is that of Ptolemy (Alexandria, ca.125). This parameter was used by Andalusi astrolabists from the 10th century onwards, even though Muslim astronomers in the early 9th century had derived more up-to-date values. These particular latitudes and the lengths of longest daylight are used already on 11th-century Andalusi astrolabes, with the exception of 33°40' for Fez and 35°20' for Ceuta, which were measured later but before ca.1200, when they were used by Abû Bakr ibn Yûsuf. (See King, In Synchrony with the Heavens, XVI-7, as well as the tables on pp. 951-957.) Such a feature well reflects the traditionalism of even the best Andalusi and Maghribi instrument-makers. The plate for Fez is remarkable in that the markings, especially for the azimuth circles near the centre, have been worn away by excessive use.
There is a fifth plate, much later than the four described above, that was probably made by the anonymous Maghribi astrolabist ca.1700. The markings are similar, with altitude circles for each 3° and azimuth circles for each 10°, with the arguments also arranged as on the plates of Abû Bakr ibn Yûsuf. The markings serve: Mecca - 22°, and Medina, the exalted (city) - 25°30'. The peg at the top ensures that the plate fits in the mater like the others.
A sixth plate has a cut-out at the top, indicating that it was probably made for a different astrolabe. Nevertheless, the engraving resembles that on the fifth plate, as do the markings and the layout of the arguments. One side, now with azimuth circles for each 5°, bears markings for the latitude of: Meknes - 34°. The other side bears a special combination of curves labelled "for all latitudes" (li-jamî' al-'urûd). These were devised by the Andalusi astronomer Ibn Bâsô ca.1300, and were often incorporated on later Western Islamic astrolabes. With such a plate, the various problems of coordinate conversion that are basic to spherical astronomy can be solved for any latitude. (On this plate see King, In Synchrony with the Heavens, X-5.2, citing the recent publications of Professor Emilia Calvo.)
The back of the mater is engraved with a minimum of markings. On the upper half of the outer rim there is a pair of altitude scales labelled for each 5° and subdivided for each 1°. Inside these is a pair of circular scales showing the correspondence between the sun's position on the ecliptic and the date in the Western calendar. These are divided and labelled for each 5° and 5 days, respectively, subdivided for each 1° and 1 day (with appropriate accommodations for months that have other than 30 days). The names of the months are standard on Western Islamic astrolabes (without vowels: ynyr, fbrâyr, mârs, abrîl, mâyh, yûnyh, yûlyh, a-gh-sh-t, sh-tnbr, uktûbr, nûnbr, djnbr). (On such scales, whose origin is still debated, see King, In Synchrony with the Heavens, X-4.7.) The equinox is at March 8.5, which implies a date of ca.1700. Inside these scales below the horizontal diameter is a double shadow square for a gnomon length of 12 digits, with scales divided and labelled for each 3 digits and subdivided for each 1 digit. (For the first history of such markings, which were devised in 9th-century Baghdad, see ibid., XIIa-A).
The alidade is an incompetent modern replacement (there is no fiducial side), and the ensemble is held together with a modern (over-long) bolt and wing-nut.
In short, this is a composite piece of substantial historical interest. It seems that a competent Maghribi astrolabist ca.1700 prepared a mater in the tradition of Abû Bakr ibn Yûsuf and a rete in the tradition of al-Khamâ'irî essentially to accommodate an incomplete set of four plates made by Abû Bakr ibn Yûsuf himself.
Bibliography and bibliographical abbreviations:
Brieux & Maddison, Répertoire: Alain Brieux and Francis Maddison, Répertoire des facteurs d'astrolabes et de leurs oeuvres, in press (Paris: C.N.R.S.)
Calvo, Ibn Bâso's Universal Plate, A-B: Emilia Calvo Labarta, Abû 'Alî al-Husayn ibn Bâso (m. 716/1316): Risâlat al-Safnha al-jâmi'a li-jamî' al-'urûd (Tratado sobre la lámina general para todas las latitudas) , Madrid: Consejo Superior de Investigaciones Cientmficas and Instituto de Cooperacisn con el Mundo Árabe, 1993, and eadem, "Ibn Bâso's Astrolabe [Plate] in the Maghrib and East", in From Baghdad to Barcelona. Studies in the Islamic Exact Sciences in Honour of Prof. Juan Vernet, Josep Casulleras and Julio Samsó, eds., 2 vols., Barcelona: Instituto "Millás Vallicrosa" de Historia de la Ciencia Árabe, 1996, II, pp. 755-767
Debeauvais & Befort, Astrolabes de Strasbourg: Francis Debeauvais and Paul-André Befort, cueillir les étoiles - Autour des astrolabes de Strasbourg, Strasbourg: Amis des instruments des sciences et des astrolabes, 2002
Gunther, Astrolabes of the World: Robert T. Gunther, The Astrolabes of the World ... , 2 vols., Oxford: Oxford University Press, 1932, repr. in 1 vol., London: The Holland Press, 1976
King, "Astronomy in the Maghrib": David A. King, "On the History of Astronomy in the Medieval Maghrib", in Études Philosophiques et Sociologiques Dédiées à Jamal ed-Dine Alaoui, Fez, 1998, pp. 27-61
King, In Synchrony with the Heavens: idem, In Synchrony with the Heavens - Studies in Astronomical Timekeeping and Instrumentation in Medieval Islamic Civilization, 2 vols., 1: The Call of the Muezzin (Studies I-IX), and 2: Instruments of Mass Calculation (Studies X-XVIII), Leiden: Brill, 2004-05
Mayer, Islamic Astrolabists: Leo A. Mayer, Islamic Astrolabists and Their Works, Geneva: Albert Kundig, 1956. [Long out-dated but soon to be replaced by Brieux & Maddison, Répertoire]
Michel, "Astrolabe marocain": Henri Michel, "Sur un astrolabe marocain", Sefunim (National Maritime Museum, Haifa) 3 (1969-71), pp. 15-21, and pl. III, and "Beauté archaïque des astrolabes", ibid., p. 47 and pls. VII-1A-B
Vernet & Samsó, eds., El legado científico andalusí: El legado científico andalusí, Juan Vernet and Julio Samsó, eds., Madrid: Ministerio de Cultura, 1992. [A catalogue of an exhibition at the Museo Arqueolsgico Nacional, Madrid, April-June, 1992]
In particular, the astrolabes of al-Khamâ'irî were often imitated, but unlike the works of the master, the 20-odd copies are all unsigned and undated. Also, it is not obvious whether they were made in al-Andalus (that part of the Iberian peninsular still in Muslim hands at a given time) or in the Maghrib. Nevertheless, they maintain the excellence of al-Khamâ'irî's astrolabes and their intricate workmanship. On the other hand, since all these instruments are engraved in an elegant Maghribi kûfî script, which barely changed over the centuries, these unsigned instruments are extremely difficult to date. In general, the more careful the engraving, the older the piece. However, most unsigned Maghribi or Andalusi astrolabes of this type have not yet been studied in detail, so that we have no proper guidelines for researching a single piece.
In the case of the present composite astrolabe, we can identify four plates that can be dated ca.1200 and attributed to Abû Bakr ibn Yûsuf, and two plates that must be considerably later. Whilst the markings inside the main frame or mater at first sight could be dated ca.1200, the date of the equinox on the back suggests a later date of ca.1700. Alas, the instrument does not speak. It has not been professionally examined and a detailed description based on photographs must suffice here.
The distinctive throne consists of two waved bars facing each other and "standing" on the rim. It is partly covered with a "pair of shoulders" to which a shackle is attached. The basic design is that of Abû Bakr ibn Yûsuf, but the curious cover is of a kind not attested elsewhere and possibly served only to reinforce the frames underneath, which may be broken.
The limbus is divided and labelled for each 5°, with subdivisions for each 1°. The mater is densely engraved with standard astrological information arranged in a series of rings. For each sign of the ecliptic, the limits according to "the Egyptians" and according to Ptolemy, the lords, faces and triplicities, are given, using the last letter of the names of the planets as abbreviations. (On astrological information on astrolabes see King, In Synchrony with the Heavens, X-4.6, and the references there cited.) The markings are identical to those on various astrolabes of Abû Bakr ibn Yûsuf, notably his 1208 Strasbourg piece (on which see Debauvais & Befort, Astrolabes de Strasbourg, pp. 66-67). One does not expect this quality of engraving on a Maghribi astrolabe from ca.1700 (see below); rather, it approaches the same quality as the engraving of Abû Bakr.
The rete is typical of the school of al-Khamâ'irî (which is quite different from the retes of Abû Bakr), and indeed resembles that on his Oxford astrolabe (Gunther, no. 130). The horizontal bar is counter-changed on both sides at the ecliptic and inside the ecliptic. The lower equinoctial arc is also counter-changed twice. There is a trace of a circular frame beneath that frame. The star Regulus, whose pointer serves as a support for the lower eqinoctial arc, is placed at ca.Leo 26°, enabling us to date the rete to ca.1700. Each of the pointers bears a silver stud, in the tradition of both al-Khamâ'irî and Abû Bakr, and their predecessors in 10th and 11th-century al-Andalus and the Maghrib. There are also four silver studs on each radial axis for rotating the rete. The 6+7+6+7 = 26 stars are typical of the Western Islamic astrolabe tradition. They are as follows, arranged in the four quadrants starting at the vernal equinox on the left hand side:
batn qaytûs - \kz\K Cephei; ra's al-ghûl - \kb\K Persei; al-dabarân - \ka\K Tauri; 'ayyûq - \ka\K Aurigae; qadam al-jawzâ' - \kb\K Orionis; mankib al-jawzâ' - \ka\K Orionis / al-'abûr - \ka\K Canis Maioris; al-ghumaysâ' - \ka\K Canis Minoris; yad al-dubb - \ki\K Ursae Maioris; shujâ' - \ka\K Hydrae; rijl al-dubb - ? Ursae Maioris; qalb al-asad - \ka\K Leonis; al-ghurâb - \kg\K Corvi / al-a'zal - \ka\K Virginis; al-râmih - \ka\K Bootes; fakka - \ka\K Coronae borealis; al-hayya - \ka\K Serpentis; qalb al-'aqrab - \ka\K Scorpionis; al-hawwâ' - \ka\K Ophiuchi / wâqi' - \ka\K Lyrae; al-tâ'ir - \ka\K Aquilae; al-dulfnn - \ke\K Delphini; dhanab al-jady - \kd\K Capricorni; ridf - \ka\K Cygni; mankib al-faras - \kb\K Pegasi; dhanab qaytûs - \ki\K Ceti
Four plates bear altitude circles for each 2° labelled for each 6°, and azimuth circles above the horizon labelled for each 5°. There are special markings for nightfall (shafaq), midday (khatt al-zawâl), the prayers shortly after midday and during the afternoon (al-zuhr and al-'asr), and daybreak (fajr), and the altitude circles for argument 18° above the horizon are also marked for daybreak and nightfall. The seasonal hours below the horizon are labelled with the appropriate ordinals. The organization of the arguments for the various markings is typical of Abû Bakr ibn Yûsuf; indeed, the plates were without any doubt engraved by him. On each plate there is an inscription: for the latitude of * and all localities whose latitude is *, with maximum length of daylight * (hours and) * (minutes)". The following localities are featured:
1a - Sijilmasa - 29° - 13h 13m; 2a - Marrakesh - 31° - 14h 3m; 1b - Jerusalem - 32° - 14h 8m; 2b - Fez - 33°40' - 14h 17m; 3a - Ceuta - 35°20' - 14h 27m; 3b - Almeria - 36°30' - 14h 33m; 4a - Toledo - 40° - 14h 54m; 4b - Saragossa - 41°30' - 15h 4m
The values for maximum daylight are accurately computed for a value of the obliquity of the ecliptic of 23°51', which is that of Ptolemy (Alexandria, ca.125). This parameter was used by Andalusi astrolabists from the 10th century onwards, even though Muslim astronomers in the early 9th century had derived more up-to-date values. These particular latitudes and the lengths of longest daylight are used already on 11th-century Andalusi astrolabes, with the exception of 33°40' for Fez and 35°20' for Ceuta, which were measured later but before ca.1200, when they were used by Abû Bakr ibn Yûsuf. (See King, In Synchrony with the Heavens, XVI-7, as well as the tables on pp. 951-957.) Such a feature well reflects the traditionalism of even the best Andalusi and Maghribi instrument-makers. The plate for Fez is remarkable in that the markings, especially for the azimuth circles near the centre, have been worn away by excessive use.
There is a fifth plate, much later than the four described above, that was probably made by the anonymous Maghribi astrolabist ca.1700. The markings are similar, with altitude circles for each 3° and azimuth circles for each 10°, with the arguments also arranged as on the plates of Abû Bakr ibn Yûsuf. The markings serve: Mecca - 22°, and Medina, the exalted (city) - 25°30'. The peg at the top ensures that the plate fits in the mater like the others.
A sixth plate has a cut-out at the top, indicating that it was probably made for a different astrolabe. Nevertheless, the engraving resembles that on the fifth plate, as do the markings and the layout of the arguments. One side, now with azimuth circles for each 5°, bears markings for the latitude of: Meknes - 34°. The other side bears a special combination of curves labelled "for all latitudes" (li-jamî' al-'urûd). These were devised by the Andalusi astronomer Ibn Bâsô ca.1300, and were often incorporated on later Western Islamic astrolabes. With such a plate, the various problems of coordinate conversion that are basic to spherical astronomy can be solved for any latitude. (On this plate see King, In Synchrony with the Heavens, X-5.2, citing the recent publications of Professor Emilia Calvo.)
The back of the mater is engraved with a minimum of markings. On the upper half of the outer rim there is a pair of altitude scales labelled for each 5° and subdivided for each 1°. Inside these is a pair of circular scales showing the correspondence between the sun's position on the ecliptic and the date in the Western calendar. These are divided and labelled for each 5° and 5 days, respectively, subdivided for each 1° and 1 day (with appropriate accommodations for months that have other than 30 days). The names of the months are standard on Western Islamic astrolabes (without vowels: ynyr, fbrâyr, mârs, abrîl, mâyh, yûnyh, yûlyh, a-gh-sh-t, sh-tnbr, uktûbr, nûnbr, djnbr). (On such scales, whose origin is still debated, see King, In Synchrony with the Heavens, X-4.7.) The equinox is at March 8.5, which implies a date of ca.1700. Inside these scales below the horizontal diameter is a double shadow square for a gnomon length of 12 digits, with scales divided and labelled for each 3 digits and subdivided for each 1 digit. (For the first history of such markings, which were devised in 9th-century Baghdad, see ibid., XIIa-A).
The alidade is an incompetent modern replacement (there is no fiducial side), and the ensemble is held together with a modern (over-long) bolt and wing-nut.
In short, this is a composite piece of substantial historical interest. It seems that a competent Maghribi astrolabist ca.1700 prepared a mater in the tradition of Abû Bakr ibn Yûsuf and a rete in the tradition of al-Khamâ'irî essentially to accommodate an incomplete set of four plates made by Abû Bakr ibn Yûsuf himself.
Bibliography and bibliographical abbreviations:
Brieux & Maddison, Répertoire: Alain Brieux and Francis Maddison, Répertoire des facteurs d'astrolabes et de leurs oeuvres, in press (Paris: C.N.R.S.)
Calvo, Ibn Bâso's Universal Plate, A-B: Emilia Calvo Labarta, Abû 'Alî al-Husayn ibn Bâso (m. 716/1316): Risâlat al-Safnha al-jâmi'a li-jamî' al-'urûd (Tratado sobre la lámina general para todas las latitudas) , Madrid: Consejo Superior de Investigaciones Cientmficas and Instituto de Cooperacisn con el Mundo Árabe, 1993, and eadem, "Ibn Bâso's Astrolabe [Plate] in the Maghrib and East", in From Baghdad to Barcelona. Studies in the Islamic Exact Sciences in Honour of Prof. Juan Vernet, Josep Casulleras and Julio Samsó, eds., 2 vols., Barcelona: Instituto "Millás Vallicrosa" de Historia de la Ciencia Árabe, 1996, II, pp. 755-767
Debeauvais & Befort, Astrolabes de Strasbourg: Francis Debeauvais and Paul-André Befort, cueillir les étoiles - Autour des astrolabes de Strasbourg, Strasbourg: Amis des instruments des sciences et des astrolabes, 2002
Gunther, Astrolabes of the World: Robert T. Gunther, The Astrolabes of the World ... , 2 vols., Oxford: Oxford University Press, 1932, repr. in 1 vol., London: The Holland Press, 1976
King, "Astronomy in the Maghrib": David A. King, "On the History of Astronomy in the Medieval Maghrib", in Études Philosophiques et Sociologiques Dédiées à Jamal ed-Dine Alaoui, Fez, 1998, pp. 27-61
King, In Synchrony with the Heavens: idem, In Synchrony with the Heavens - Studies in Astronomical Timekeeping and Instrumentation in Medieval Islamic Civilization, 2 vols., 1: The Call of the Muezzin (Studies I-IX), and 2: Instruments of Mass Calculation (Studies X-XVIII), Leiden: Brill, 2004-05
Mayer, Islamic Astrolabists: Leo A. Mayer, Islamic Astrolabists and Their Works, Geneva: Albert Kundig, 1956. [Long out-dated but soon to be replaced by Brieux & Maddison, Répertoire]
Michel, "Astrolabe marocain": Henri Michel, "Sur un astrolabe marocain", Sefunim (National Maritime Museum, Haifa) 3 (1969-71), pp. 15-21, and pl. III, and "Beauté archaïque des astrolabes", ibid., p. 47 and pls. VII-1A-B
Vernet & Samsó, eds., El legado científico andalusí: El legado científico andalusí, Juan Vernet and Julio Samsó, eds., Madrid: Ministerio de Cultura, 1992. [A catalogue of an exhibition at the Museo Arqueolsgico Nacional, Madrid, April-June, 1992]