The earliest archaeological evidences for the plane astrolabe are Arabic and date from the 9 th century. However, as noted by Fuat Sezgin, two treatises on the uses of the astrolabe predate them: the oldest is a Greek treatise by John Philopon (6 th c.) known in the Arab tradition under the name of al-Biṭrīq; the other is a Syriac treatise attributed to the Syrian Orthodox bishop Severus Sebokht (d. after 665) which Fuat Sezgin presents as "der älteste namentlich bekannte Astronom auf islamischem Gebiet" (Sezgin, 1978, p. 111).

In the light of a still unpublished critical edition of Severus Sebokht's Treatise on the Astrolabe and a very recently published 7 th c. Syriac Letter on klimata (Defaux & Villey, 2023), this contribution will show that the Greek and Syriac astrolabes of the 6 th and 7 th centuries were quite different from those found later in a Syrian-Arab context; that the astrolabe was probably the only means of performing complex astronomical calculations for the Syriac scholars of Cyprus and Syria; and finally that the Umayyads were undoubtedly familiar with the astrolabe from the middle of the 7 th century, even before the start of their caliphate.