Astronomers at work. Psalter of Blanche of Castille. Paris, Bibliothèque de l’Arsénal, ms. 1186, fol. 1r (Paris, ca. 1226-32). The central figure is making an observation using an astrolabe. The figure on the left appears to be recording the result of the observation while the one on the right consults a text, possibly a very early ephemerides or set of astronomical tables.