In 1676, an Ottoman perpetual calendar titled "Commentarius in Ruzname Naurus, sive, Tabulae aequinoctiales novi Persarum & Turcarum anni" was published in Augsburg. Accompanying this publication was a commentary authored by Georg Hieronymus Welsch (d. 1677) on behalf of Christoph Weikmann (d. 1681), a merchant in the Imperial Free City of Ulm. The authorship of the Ottoman calendar became a subject of fervent debate among orientalists and historians of science. Notably, German orientalist and Ottoman Empire historian Franz Babinger (d. 1967) regarded this Latin commentary as a significant source in the debate, even though he himself did not analyse the text. Babinger further asserted that the commentary is evidence of Hieronymus Welsch's proficiency in Ottoman Turkish, as it would be essential for him to produce such a commentary.

The presentation, -and the forthcoming book chapter- entitled The Reception of an Ottoman Perpetual Calendar in 17th-Century Europe: Georg Hieronymus Welsch’s “Commentarius in Ruzname Naurus” by Assist. Prof. Gaye Danışan (Istanbul University) and R.A. Kutsi Aybars Çetinalp, PhD(c) (Istanbul Technical University), provide a significant revelation regarding the so-called Latin commentary.  Through a comparison of the Latin and Ottoman texts, Danışan and Çetinalp convincingly demonstrate that the commentator, Georg H. Welsch, lacks proficiency in Ottoman Turkish. This ground-breaking insight settles the debate surrounding the authorship and the perceived significance of the Latin commentary in the context of the Ottoman calendar. This study was part of a project entitled “A Comparative Study on Theoretical and Practical Aspects of Scientific Activity in the Ottoman Empire: Annual and Perpetual Calendars (1550-1710)”, which was founded by the Scientific and Technological Research Council of Türkiye from 2020 to 2022 (project no: 119K827).

Çetinalp was also among the organizers of the international congress “Channels of Transmission of Astronomical Knowledge in the Ottoman World (14th-18th Centuries)”, where the aforementioned study was presented. Istanbul Technical University, in collaboration with other organizers, including the Istanbul University Department of History of Science, Institut Français d’Études Anatoliennes and Turkish Historical Society (TTK), was also present in the organizing committee, whereas Prof. Tuncay Zorlu, Assoc. Prof. Hasan Karataş and Dr.  Saltuk Duran were among the members of the scientific board. The congress, held from 21-24 November, brought together 40 speakers from 14 countries to explore the Ottoman Empire’s role in the transmission of astronomical knowledge.

Following this intellectually fruitful congress, an enchanting epilogue took place in the form of a workshop on 28 November, titled "Tracking Astronomical Instruments Through Ottoman World and Beyond Workshop." in which Kutsi A. Çetinalp participated as a teaching assistant to Prof. Jan P. Hogendjik, the Department of Mathematics at Utrecht University. In the workshop, 80 participants from various fields came together to engage in hands-on activities, from deciphering abjad numbers to disassembling and examining astrolabes, calculating the date and length of a day by an astrolabe, using solar and lunar calendars with volvelles.

Further information about the congress can be found in: