Besides, Flammarion observed the Moon and planet Mars. He published several popular books (L'astronomie Populaire in 1879, of which over 100,000 copies were sold and an English translation by J.E. Gore appeared in 1894, as well as a book on Mars, supporting the existence of "canals", built by an advanced civilisation), and encouraged amateur astronomy. In 1877, Flammarion founded the Astronomical Society of France. In 1882, he was donated a private observatory and estate by a M. Meret who admired his work.
In 1922, he was made a Commander of the Legion of Honor for his astronomical life-work.
In 1921, Flammarion added M104 to the Messier
catalog. He had found Messier's handwritten
position in his personal copy of the catalog, which he happened to possess.
M104 could be identified with William Herschel's
H I.43 or NGC 4594.