The subject of this book is the Western astronomical tradition from ancient Babylonia to the European Renaissance, with special emphasis on the Greek period. Throughout the book two questions constantly recur: what evidence permits us to reconstruct the astronomy of the ancient past? How was astronony actually practised? The book is meticulously documented and makes full use of primary sources as well as modern historical scholarship. It is richly illustrated and is unusual for its attention to the material culture of ancient astronomy. The most striking aspect of the book is its attention to astronomical practice.