Because of Le Verrier’s lack of interest in astrophysics, an enterprising astronomer, Jules Janssen (1824-1907), was free to create an observatory dedicated to this domain. He met with unexpected success since he managed to furnish it with a double-refractor telescope, the largest in the world for one year, whose objective lenses for visual observation and photography have a diameter of 83 cm and 62 cm.

caption : Solar photography refracting telescope in front of a barrack around 1878 - credits : Observatoire de Paris