Can an astronomical instrument be religious? Wooden quadrants from the Late Ottoman Empire.

Yasemin Akçagüner, Columbia University, New York
Recipient of SIS grant 2022


In 2018, Silke Ackermann posed the following question in an SIS Bulletin article: “Can an astronomical instrument be religious?” [1]. In many museum collections today, scientific instruments from the Middle East and North Africa are placed within Islamic galleries or labeled as Islamic instruments, while instruments from the Western world are largely labeled and exhibited according to the nation-states or polities in which they were crafted or manufactured. Such is the case with a wooden astrolabic quadrant exhibited in the Albukhary Foundation Gallery of the Islamic World at the British Museum (Figure 1), an instrument whose functions and possible use in trade across the Ottoman Empire complicates its straightforward designation as an Islamic instrument used for determining prayer times.

Figure 1: Wooden quadrant from AD 1891-92 (AH 1307-08).

Figure 1 shows a wooden quadrant from AD 1891-92 (AH 1307-08), was made in Damascus, Syria and “would have been used by an Ottoman merchant or official. It contains a correspondence table for comparing hijri (the Islamic lunar calendar), Coptic, French Julian and financial calendars, demonstrating the coexistence of different faiths and calendars with the Islamic world,” the display label reads [2]. This particular quadrant points to uses of the instrument beyond timekeeping for the purposes of establishing prayer times and postulates a use for the quadrant in daily affairs of commerce and trade in the late nineteenth century, a claim that would benefit from further exploration.

Intrigued by the instrument from the British Museum, I have set out to explore others of the same kind, specifically wooden quadrants from the Ottoman Empire. Owing to the Empire’s longevity (from the fourteenth to the twentieth century) and its geographic span (ranging from the Balkans to the Red Sea at its height in the early seventeenth century), it offers an ideal laboratory for studying scientific instruments across the Middle East and North Africa, both in their variety and similarity across time and space. While the history of Islamic astronomical instruments in the medieval period have been studied extensively by David King and Emilie Savage-Smith [3], late Ottoman astronomical instruments are only recently coming into the limelight thanks to the works of Feza Günergun and Gaye Danışan. Feza Günergun’s recent research has shown the role of artisan-scholar collaboration in the making of Ottoman astronomical instruments, and specifically astrolabic quadrants – an instrument largely understood to be used by muwaqqits, or timekeepers of imperial mosques, for the purpose of determining prayer times [4]. Yet the scope of the possible uses of these quadrants and who might benefit from their uses remains to be explored: Beyond timekeeping for the purposes of establishing prayer times, how were these quadrants used?

To be able to answer that question we first need to know the answers to a number of more basic questions: Who could learn to use the quadrant? And how did they learn it? Was the learning process tactile, textual or in some other form? Is the large number of surviving manuscripts with instructions for the use of this instrument a testament to the instrument’s use by a wider group of lettered people that included not only the timekeepers of mosques, but also seafarers and merchants for instance? Could any lettered person hope to learn how to use the instrument simply by reading through one of these manuals?

With the support of an SIS grant I am comparing and contrasting the inscriptions on various quadrants as well as manuals for the instruments found in select collections in the UK. These include the Oxford HSM, Cambridge Whipple Museum and the British Museum, alongside a number of manuals, in manuscript form, on the uses of these instruments in the relevant University and British Library collections. One such manuscript is from the British Library Oriental Manuscripts collection (Figure 2).

Figure 2: British Library, Oriental Manuscripts, MS Oriental 14275.

British Library, Oriental Manuscripts, MS Oriental 14275 (see figure 2) was copied in the year AH 1268 (1851-52 AD). It describes the parts of the quadrant and provides instructions on how to use the instrument to determine time in two parts. Part one, Terceme-i Gedūsī li’l-Muḳanṭarāt (Translation of Gedusi on the Muqantarat) describes the parts and function of the astrolabic face of the quadrant whereas part two, Terceme-i Gedūsīli’l-Ceyb (Translation of Gedusi on the Ceyb) explains the sine face of the quadrant. The text is a translation from the Arabic original into Ottoman Turkish by the author himself. The first part refers to resm or images that are meant to accompany the text but are missing from this copy. The text relies on the drawings of the quadrant for its explanation, which is perhaps a later phenomenon in the development of such quadrant manuals with earlier copies such as the Risale-i Ceyb (Treatise on the Sine Quadrant) in the sixteenth-century MS Selden Superius 97 (ff 34-59, Bodleian Library, Oxford University) featuring no such images or mentions of images. This points us towards the potential use of technical drawings as tools for the practical teaching of astronomy in the nineteenth-century Ottoman Empire.

In a follow up article in the SIS-Bulletin I hope to offer a more detailed and comprehensive analysis of the quadrants and manuals found in the above mentioned collections.

Yasemin Akçagüner is a doctoral candidate in the History department at Columbia University, New York.


[1] S. Ackermann, ‘Gerard Turner Memorial Lecture: In the Service of Religion? ‘Islamic Science’ in the Museum’, In: Bulletin of the Scientific Instrument Society No. 139, (December, 2018).

[2] Astrolabic quadrant, 1997, 0210.1, The British Museum. For the curator’s comments see

[3] King, David A. “Quadrants.” In Islamic Astronomy and Geography, 167–69. London: Routledge, 2022; and Savage-Smith, Emilie, and Andrea P. A. Belloli. Islamicate Celestial Globes, Their History, Construction, and Use. Smithsonian Studies in History and Technology, no. 46. Washington, D.C: Smithsonian Institution Press, 1985.

[4] Günergun, Feza. “Timekeepers and Sufi Mystics: Technical Knowledge Bearers of the Ottoman Empire.” Technology and Culture 62, no. 2 (2021): 348–72. See also Danışan, Gaye. “Paper Instruments in the History of Ottoman Astronomy.” Scientific Instrument Society Blog (blog), 22 February 2021.

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