Article ID: CBB436990599

A Mathematical Analysis of the Theory of Horizontal Sundials in the Ottoman Period: The Case of Risalah of Ruhama (2015)


As the prayer times are determined according the sun’s position, the theory of sundials, how to draw and design them, hold a significant place in the history of Islamic astronomy. All Muslim scientists working on applied and theoretical sciences have books on this subject. Besides, as it was a part of madrasa curriculum, there are considerably high number of unexamined books from the beginning to the end of the Ottoman period. This study is about a manuscript titled Risālah-i VaZ‘-i Ruhāma, that we received from a second-hand book seller. Its anonymous author argues that he offers a simpler way to draw sundials designed for Istanbul. The author leaves the person willing to make a sundial free to determine the height of the gnomon and he shows a practical method to draw ruhāma with the help of goniometer and ruler prepared according to the determined height. Although the article presents the mathematical bases of the method, it is unable to verify clearly how the author derived the numeric values given in the book. To the end of our study, facsimile text and its simplified transcription are attached.

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Authors & Contributors
Savoie, Denis
Zhang, Yang
Himanshi Khurana
Jean-Marie Michel
Stefano Barbolini
Sergei J. Maslikov
Journal for the History of Astronomy
Studia Historiae Scientiarum
Nazariyat: İslam Felsefe ve Bilim Tarihi Araştırmaları Dergisi (Journal for the History of Islamic Philosophy and Sciences)
Tarikh-e Elm (The Iranian Journal for the History of Science)
Ziran Kexueshi Yanjiu (Studies in the History of Natural Sciences)
Science History Publications
Instruments, astronomical
Scientific apparatus and instruments
Time measurement
Time measuring instruments
Przypkowski, Tadeusz Konrad
Seydī 'Ali Re'īs
Ramsden, Jesse
Muhtar Pasha, Ahmed
La Hire, Philippe de
Galilei, Galileo
Time Periods
18th century
17th century
20th century
16th century
Ottoman Empire
Rhodes (Greece)
Beijing (China)
Nanjing (China)
Hermitage Museum (Saint Petersburg)
Palermo. Osservatorio Astronomico

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