Classes did not always end with nightfall. In his account of activities connected with the arts, Hugh of Saint Victor claimed, ‘Often I kept watch outdoors through the winter nights like one of the fixed stars by which we measure time.’ Astronomy was clearly distinguished from other subjects by its focus on bodies visible in the sky. Yet the study of the stars had applications connected with both geometry and arithmetic, in the exploration of space and calculation of time. The rather exotic nature of this subject may have contributed to a higher level of interest in this art than those of either arithmetic or geometry. Certainly the subject received the attention of artists in surviving books about the heavens and the teaching of astronomy, as well as in the cycles of the arts in sculpture and metalwork. The decision to decorate books on astronomy may also have been related to the nature of the art as a visual discipline, based on observation of the night sky. As Rembrandt Duits has shown, a range of illustrated guides to the constellations were available to the twelfthcentury student. However these images were part of a long tradition of illustration and the volumes did not require (and often would not have helped) the student to locate the stars. Thus, as with the art of geometry, a tension is evident in the surviving manuscripts between studies outside the classroom and the texts read and discussed within it. The many images of constellations and planets will not be considered here. Instead this chapter will explore the allegorical figures of Astronomy and illustrated diagrams that show processes apparently used in astronomical study.

All the surviving allegories of Astronomy show the art with heavenly bodies. In the earliest version, in the mid-ninth-century Boethius manuscript now in Bamberg, Staatsbibliothek Msc. Class. 5, fol. 9v, Astronomy holds a torch and has the sun and moon above her head. These bodies are behind her, but her eyes are nevertheless raised to the sky. In the twelfth-century sculpted cycles Astronomy often points to the heavens. On the west facade of Chartres Cathedral the figure (in the outer archivolt, fourth from the right) raises her right hand and looks upwards (Fig. 2), at Loches the art points to two round objects next to her head and turns towards them and at Déols the destroyed figure also pointed upwards to a star.