When the National Convention instated the Bureau des longitudes in 1795, it added to the institution’s nautical missions a responsibility for the diffusion of Enlightenment and turned it into one of the main institutions for the popular diffusion of astronomy. This paper sheds light on three stages of this transformation. The astronomer Jérôme Lalande first continued his work of opening up the science of the Heavens to a wider public until his death in 1807. François Arago then gave the publications in the Annuaire du Bureau des longitudes (almanac and calendar published annually from 1795) their fame, and their impact can be measured in the writings of Camille Flammarion or Jules Verne. However from 1854 on, French astronomy was firmly led by Urbain Le Verrier who cared little for the diffusion of its works, leaving that task to professional popular science writers. In the end the astronomers from the Bureau des longitudes, united against Le Verrier, went back to the tradition of diffusion.