Astronomy became popular long before Camille Flammarion’s celebrated works of popular science. Astronomical science must be understood by all, educated bourgeoisie or worldly elite, and in particular by the people. Its place within the disciplines taught and the professional or utilitarian publications that started to multiply at the beginning of the 19th century is original. The open class in popular astronomy given by François Arago at the Paris Observatory is very different from the course offered the Parisian working-class by Auguste Comte, but for both these social reformers, the observation and knowledge ofthe Heavens are thought to participate in the empowering of the people. As for the Christian philosophers, they see in astronomy a way to resist popular beliefs and superstitions while maintaining the social harmony – class hierarchies – that are God’s will.