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Omar Khayyam's observatory in Isfahan?
Anyone happen to know if any reports exist about this observatory - beyond basic reports of its existence and the fact of Khayyam's Jalali calendar being produced? Would be intereseted in any accounts, contemporary or modern, of the observatory's likely construction / structure, and of any details of instruments or methodology used. If not specifically about Isfahan, would also be interested in any material on methods of astronomic observation / recording predating the telescope.