The Sultanate of Oman is possibly unique in using stars to time the allocation of water in the traditional irrigation systems called aflāj (s. falaj), which are still an important part of Omani culture and sense of national identity. This is a rapidly disappearing oral tradition that has hardly been known about outside Oman prior to this study. The need for timing water shares is explained and the methods of stargazing described. The identities of the stars, their Omani names and the relationship with modern star names are discussed.