In many books on the history of lighthouses, Augustin Frenel's lenticular apparatus marked the beginning of a new era in maritime signalling. An analysis of the scientific community in which Frenel worked shows that the construction of the French network in the early nineteenth century crystallized a body of knowledge shared by sailors, scholars and engineers. The Commission des phares, responsible under the Empire and the Restoration for a national lighthouse programme, conceived the maritime border as a controlled celestial system. It drew an ideal map of the French coast, using objects and words from astronomy. The paradigm of 'star-lighthouses'? was to be the base of French maritime signalling policy for seventy years. This paper highlights the original features of this policy compared to the more pragmatic British and US model. With the appearance of new technical systems in the late nineteenth century, especially electric lights, the coastal network was redesigned around a new paradigm: the flashlight.