This important astrolabe is one of two known pieces dedicated to the Ottoman Sultan Bayezid II (r. 1481-1512). There are no other astrolabes dedicated to an Ottoman sultan, not even in the Topkapi Sarayi Museum.
This piece represents the beginning of a new Ottoman tradition in modestly-decorated astrolabes, a tendency to be observed already in various earlier Syrian pieces made by professional astronomers themselves rather than by professional craftsmen. The other, made in the previous year by Shukrallah Mukhlis Shirwani, is more in the Persian tradition and is more ornately decorated in a distinctive style; it is preserved in the Museum of Islamic Art in Cairo1. The makers of both arts are not otherwise known (see further below).
The history of early Ottoman astronomy in general (from the fourteenth to the early sixteenth century) has not yet been properly researched. It was influenced by the Seljuq Turkish tradition (Anatolia, thirteenth century) of which very few sources and not a single instrument survive; by the colourful Mamluk tradition (Egypt and Syria, thirteenth-fifteenth centuries)2, and by the vigorous Ilkhanid and Timurid traditions (Iran and Central Asia, thirteenth-fifteenth centuries)3. The sources for Ottoman astronomyhave recently been properly documented for the first time4, and the amount of possible research for the future is daunting.
The interest of Bayezid II for astronomy is well-known5. The institutions of court munajjims (astronomers-astrologers) and mosque muwaqqits (timekeepers) were well established in his time. The sultan studied mathematics and astronomy with his private teacher, who was none other than Miriam Chelebi, the grandson of Qadi Zade al-Rumi, director of Ulugh Beg’s observatory at Samarqand. Numerous astronomers dedicated their work to Bayezid, including treatises on instruments and highly sophisticated tables. He himself commissioned his teacher to prepare a Persian commentary to the astronomical tables of Ulugh Beg.
The early Ottoman tradition of instrument-making (fourteenth-sixteenth centuries) is represented only by these two preparation pieces for Bayezid II. All other surviving Ottoman astrolabes are later than these two, indeed at least a century later. Out of a total of some 30-odd pieces6, none shows any indication of having been influenced specifically by either of those two pieces.
The astrolabe of Bayezid II
The workmanship is competent but, primarily, this is an astrolabe designed to be used. The engraving, in Kufic, is elegant and distinctive. The Arabic alphanumerical (abjad) notation is used throughout, except for the date, which is written in Hindu-Arabic numerals.
The throne is undecorated, with lobes on either side of the upper lobe and smaller protrusions at the far left or right. The suspension apparatus, a shackle and ring, is attached at the top of the throne.
The matter bears a circumferential scale divided for each 5° and subdivided for each 1°, labelled 5° - 10° - 5° - 20° - … - 5 -  60°. The base circles for the equinoxes and two solstices are engraved in the inside of the mater. (This was a common practice, which enabled additional markings to be added at will).
The rete is of unusual design, it is simply decorated. The horizontal diameter is rectilinear (not counter changed), as was standard on Early Islamic astrolabes. The vertical axis is complete, but incorporates some decorative features. Above the centre there is a heart-shaped, or perhaps rather hoe-shaped, frame in the upper-half of the ecliptic (not known on any other astrolabe). Above this is a flower-shaped design with six petals, at the centre of which is a silver knob, which serves, along with three others, two at either end of the horizontal diameter and another below the centre, to turn the rete over the appropriate plate. The earlier development of these designs can be traced (see the commentary below).
The scale of the ecliptic is divided for the zodiacal signs, whose names are the standard forms:
Al-hamal – al-thawr – al-jawza’ – al-saratan – al-asad – al-sunbula – al-qaws – al-jady – al-dalw – al-hut
And each sign is divided into five unlabelled 6°-intervals. The star-pointers are shaped like jesters’ hats, developed – as if by lack of starching – from the dagger-shaped pointers on early Eastern Islamic astrolabes. They serve 15 named stars, here listed in order of increasing right ascension (counter-clockwise from the vernal equinox) and identified8:
1… al-dabara n 24/18 alpha Tauri
2…. Rijl al-jawza’ 37/19 beta Orionis
3…(al-shi’ra) al-yamania… 39/23 alpha Canis Maioris
4…(al-shi’ra) al-sha’miya 39/23 alpha Canis Minoris
5…qalb-al-asad 26/30 alpha Leonis
6…(al-simak) al-a’zal 29/39 alpha virginis
7…(al-simak) al-ramih 29/39 alpha Bootis
8…’unuq (al-hayya) 12/196 alpha Serpentis
9…--- fakka [ineligible word]#2/45 alpha Coronae Borealis
10… qalb al-‘aqrab 30/48 alpha Scorpii
11… (ra’s) al-hawwa’ 11/51 alpha Ophiniuchi
12…(al-nasr) al-ta’ir 13/54 alpha Aquilae
14… dhanab al dajaja 6/56 alpha Cygni
15… mankib (al-faras) 17/62 beta Pegasi
#One might expect al-munir min al-fakka or nayyir al-af-fakkar
There are three plates with five sides engraved with altitude-circles for each 3°, labelled for each 6°. The altitude arguments are engraved in lined ‘cartouches’ on the left and right, continuing down the centre (i.e. up the meridian) to the zenith, which is labelled 90° within the altitude circle for 84°. Such cartouches are found already on some of the plates of 10th century astrolabes. The east – and west – points are labelled al-machriq and al-maghrib below the horizon. There are no azimuth curves. The curves for the seasonal hours below the horizon are labelled 1, 2, …, 12. (On the plate for 41;30° the ‘1’ has been repeated but the mistake realised: the numbers run 1-1-2-3-4-6-…). The astrolabe markings serve latitudes:
33° 36° 39° 40° 41° 30.
The latitudes are indicated by the expression ‘ard--, ‘latitude--. No localities are associated with these, but see the commentary.
On the back of the plate for latitude 33° is a set of half- horizons arranged in four quadrants and marked for latitudes:
28°/38° 33°/48° 32°/45° 30°/43°.
The back is simply executed. Above the horizontal diameter there are two altitudes scales with divisions labelled for each 5°, subdivided for each 1°.
In the upper left quadrant is a sexagesimal (base 60) trigonometric grid with equi-spaced horizontal and vertical lines drawn for each 3 units. In the upper right quadrant the dedication is engraved within a double circle. The rim of the lower left quadrant is devoid of markings and in this quadrant the name of the maker is engraved on a single line. The rim of the lower right quadrant is marked with a scale for shadows to base 12 and is labelled zill-I asabi, ‘shadow in digits’. The sale begins at the bottom and is marked up to 25 digits, each 5 being labelled, with subdivisions for each 1 unit. Inside this quadrant there is a shadow square to base 12 with horizontal and vertical scales divided and labelled for each 3 units (digits), subdivided for each single unit.
The dedication reads:
Li-rasm khizanati ’l-sultani ‘l-a’zam al-sultan ibn al-sultan sultan Bayazid ibn Muhammad Khan khallada [‘llah] mulkahu
‘By order of the Treasury of the Greatest Sultanm sultan son of sultan, Sultan Bayezit son of Mehmet Khan – may [God] make his dominion last for ever.’
The inscription naming the maker reads:
Sana’ahu ‘l-Ahmah al-Nujumi al-Rumi fi sanati 911 Hijriyya
‘Constucted by al-Ahmar al-Nujumi al-Rumi in the year 911 Hijra’
The date is written in Hindu-Arabic numerals and corresponds to 1505/06 A.D.
The alidade is not counter-changed and is decorated with clef-shaped ends. There is a sexagesimal scale on one half of the alidade, labelled 6-12-…-54-60, for use in conjunction with the trigonometric quadrant on the back.
The decoration of the rete
The basic simplicity of the rete is in the tradition of the non-presentational pieces from the Mamluk Syria, such as the one made by the Damascus Astronomer Ibn-al-Shatir in 726 AH/1325-26 AD9. The flower on the rete can be traced back to the decorative quatrefoil on the spectacular astrolabe of the astronomer al-Khujandi, made in Baghdad in 374 AH/984-85 AD10.
This quatrefoil, probably Byzantine in inspiration, is found on several astrolabes from the Islamic East over the centuries, notably on one made in Isfahan in 618 AH/1223-24 AD11. On this piece the quatrefoil occurs above a frame shaped like the side cross-section of an artichoke, which encloses the star-pointed for Vega, graphically represented as an eagle. Various later Eastern Islamic show this combination of motifs, which on this astrolabe for Bayezid II appear in a much simplified form. The Isfahan astrolabe mentioned above also has a star-pointer of the jester-hat variety.
The latitudes used for the plates
The plate for 33° could serve Damascus and Baghdad; 36 °– Aleppo and Mosul; 39° – Kayseri, Konya (?) and Ankara; 40° – Bursa and Suvas. The plate for 4130’ was clearly intended for Istanbul, although the latitude of that city is correctly 41° 2’. There were several problems with medieval values for the latitude of Constantinople, which was often taken as 45° 12 and Ottoman astronomers were the first to measure it properly.
For comparison we note the latitudes serves by the plates on the other astrolabe dedicated to Bayezid II, namely 21°, 30°, 33°, 36°, 38°, 40° and 41°. The first and second would have been intended for Mecca and Cairo, the last for Istanbul ad 38° for Konya and Malatya.
The maker of this astrolabe, al-Ahmar al-Rumi al-Nujumi, is unknown to the modern literature on Islamic instrumentation13. His name is unusual and means ‘the red one’. Nevertheless, the name Ahmar is an attested Muslim name. The epithet al-Rumi indicates that he was a Turk from Central Anatolia14. The epithet al-nujumi indicates that he was an astronomer, yet he is not mentioned in the recently-published bio-bibliographical survey of Ottoman astronomers and their works15 which means that he did not author any treatises. Likewise the maker of the other astrolabe dedicated to Bayezid II is otherwise unknown.
1. Gunther 1932, I, p. 126, no.12. The piece has been misdated to (8)91 AH/1496 AD., but the date is clearly 910 AH/1504-05 AD. See the illustrations of the front and back (to Hartner 1938) in Pope 1938/39, III, p.2518, and VI, pl.1399, and Mayer 1956m p.83, for further bibliography.
2. See King 1983.
3. See Kennedy 1968 and 1986.
4. Ihsanoglu 1997.
5. See Adnan 1939, pp.28,35,43-52; the numerous references in Ihsanoglu 1997, II, p. 992; as well as King 1980, pp.247-248.
6. A preliminary catalogue of these has been prepared in Frankfurt as part of la larger ongoing project to catalogue all medieval Islamic and European instruments (see King 1991a). Several Ottoman astrolabes are featured in Dizer 1986 and Mouliérac 1989. A handlist of astrolabes is in Price et al. 1973.
7. See Irani 1955.
8. The numbers are those in Kunitzsch 1990, pp.158-161 and Kunitzsch 1959 pp.59-96, and p. 217 (for no.8).
9. Paris 1991, p.435 (no.331).
10. King 1995, pp.90 and 82-89, no.2.
11. Gunther 1932, I, pp.118-120, no.5.
12. Kennedy & Kennedy 1987, pp.93-94.
13. The basic reference work is still Mayer 1956.
14. Article ‘Rumi’ in EI.
15. See no.5 above.
This note was prepared with the kind assistance of Professor David A. King, Frankfurt.