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[Astrolabe]
- Author: [Anonymous]
- Publication date: c1250.
- Physical description: Brass. The entire instrument is in western kufic script. It was made in one piece. The throne is decorated with geometric shapes in different techniques on each side. While the decoration on the recto is engraved, the one on the verso is embossed. A plain shackle with a ring on top is attached to the plate by a pin. Recto Engraved along the circumference of the recto is four sets of 90-degree scales arranged in four quadrants. Each scale is divided into 5-degrees and labelled with alphanumeric notation (i.e., abjad) and further subdivided into 1-degree. Inside the scales is a double universal astrolabe projection of the same style which was first designed by the 11th-century Andalusian astronomer al‐Zarqālī known as saphea azarchelis. The first projection represents the celestial coordinates. The second is superimposed at an angle of approximately 23.5 degrees and represents the ecliptic coordinates. The equatorial longitudes are labelled in abjad for every 5-degrees from 5- to 180-degree and in reverse 185- to 360-degree along the equator. The equatorial latitudes are also labelled for 5-degrees from the equator to the poles in the order of 5-10-5-20-5-30-… instead of 5-10-15-20-25-… The poles are inscribed: The southern celestial pole - Quṭb muʿaddil al-nahār janūbī The northern celestial pole - Quṭb muʿaddil al-nahār shimālī On the ecliptic projection the ecliptic and longitude arcs for every 30-degrees are marked with arrow-shaped patterns. The poles are inscribed: The southern ecliptic pole - Quṭb falak al-burūj janūbī The northern ecliptic pole - Quṭb falak al-burūj shimālī The names of the signs of the zodiac are engraved between 35- and 40-degree ecliptic latitude curves on both northern and southern sides. They read: Signs on the southern side Jawzā - Thawr - Ḥamal - Ḥūt - Dalw - Jadī Gemini - Taurus - Aries - Pisces - Aquarius - Capricorn Signs on the northern side Qaws - ʿAqrab - Mīzān - Sunbula - Asad - Saraṭān Sagittarius - Scorpio - Libra - Virgo - Leo - Cancer There are seventeen stars that are labelled and marked by a small dot inside a circle. These are: (Starting at northern ecliptic pole towards the ecliptic) α Lyrae - wāqi‘ α Cygni - ridf α Bootis - rāmiḥ β Pegasi - mankib faras α Aquilae - ṭā’ir β Persei - ghūl α Aurigae - ʿayyūq ? - munīr al-? (Starting at southern ecliptic pole towards the ecliptic) α Carinae - Suhayl α Canis Maioris - ‘abūr β Sagittarii - ʿurqūb al-rāmī β Leonis - ṣarfa α Sagittarii - rukbat rāmī β Canis Minoris - ghumayṣā α Tauri - dabarān α Scorpionis - qalb α Virginis - aʿzal Alilade Attached by a central pin on the recto is a chamfered alidade. On the chamfer is a ruler with 5-unit divisions and 1-unit subdivisions. Each 5-unit is labelled in abjad. Divisions are engraved neatly and correspond well with the engravings on the universal astrolabe projection on the recto. Style of inscription and near-perfect match of the divisions indicate that the alidade is highly likely to be the original. Verso On the upper half of the circumference is a double 90-degree altitude scale, divided into 5-degree and labelled in abjad, and further subdivided into 1-degree. Lower half of the circumference carries non-linear shadow scales or cotangent scales for 12-base on the right and 7-base on the left. The scale for 12-base is divided and labelled for 3, 6, 9, 12, 17, 22, 27, 39, and 48 units. The scale for 7-base is divided and labelled for 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 15, 20, and 30 units. Inside these are two nested circular scales, one for the zodiac calendar and the other for the Julian calendar. The Julian calendar is also divided into 5-day intervals and labelled, and further subdivided into 1-day intervals. The inscription for the zodiacal calendar reads: al-Sunbula - al-Asad - al-Saraṭān - al-Jawzā - al-Thawr - al-Ḥamal Virgo - Leo - Cancer - Gemini - Taurus - Aries al-Ḥūt - al-Dalw - al-Jadī - al-Qaws - al-ʿAqrab - al-Mīzān Pisces - Aquarius - Capricorn - Sagittarius - Scorpio - Libra The inscription for the Julian calendar reads: August - July - June - May - April - March February - January - December - November - October - September At the centre of the verso is an orthographic projection on three quadrants while the lower right quadrant carries a sine graph (mujayyab) with 59 parallel lines for the sexagesimal (60-base) system. The divisions of the projection are labelled for each 5-degree.
- Dimensions: Diameter: 185 mm
- Inventory reference: 21900
Notes
Unsigned and undated, this single-plate astrolabe can only be dated approximately based on two indicators. The Zodiac scale and Julian calendar on the verso show that 0-degree Aries corresponds with approximately 13.8 March. This puts the possible date of construction between 1150 and 1250. The second indicator is the placement of stars on the projection on the recto. A close examination allowed us to measure the positions of the stars with a margin of error of ±1 degrees. This data was initially compared to computer assisted calculations for different dates from different centuries. The closest matches for the positions of the stars were from the 13th-century data.
Additionally, a second comparison was conducted between this astrolabe and two other universal astrolabes from the 13th century: One from 1218/19 by Muammad ibn Fattū al-Khamāiʾrī – currently in the collection of the Bibliothèque nationale de France (inv. cote Ge A 408)- and another from 1270/71 made by Ibrāhīm al-Dimashqī – which is in the British Museum (inv. 1890,0315.3). The undated astrolabe has near-match star placements with both astrolabes, although not for all seventeen stars. Mismatching stars, however, indicate later dates in comparison to Khamāiʾrī astrolabe and earlier dates to Dimashqī astrolabe. This allows us to argue that the date of construction of this astrolabe might be between 1219 and 1270, perhaps around 1250s.
The thirteenth century was a lively period for astrolabe making in the Islamic West, that is Maghrib and al-Andalus. Khamāiʾrī was arguably the most prominent of the instrument makers of his time. At least fourteen astrolabes by his hand survive, albeit most of them are planispheric astrolabes. Knowing that he signs his instruments, it would not be reasonable to assume this is one of his works. Furthermore, the rarity of surviving universal astrolabes from any period and very common features of the western kufic script which can be observed on most of astrolabes from the Islamic west prevent us to argue any possible name for its maker. It is clear that it was made in the closely followed tradition of astrolabe making in the Islamic West. Only peculiar feature is perhaps its alidade, which is almost like a triangular prism.
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Find Us
New York
PO Box 329, Larchmont, NY, USA
Opening hours, London Gallery
Monday to Friday: 10:00 – 18:00
Saturday: by appointment
Closed: all bank holidays and 1-31 August
Opening hours, New York
By appointment only