Charles Nordmann (1881-1940), an astronomer at the Observatory, was an original thinker who tried to detect, for the first time in 1901, radio waves emitted by the Sun. In 1907, he designed a photometer for the simultaneous measurement of stellar radiation in three spectral bands. This enabled him to find the temperature of different kinds of stars. A comparison with modern measurements shows that his were very good. However, this fundamental work was relatively unknown, since the Observatory’s director of the time showed no interest in it.

caption : Nordmann Photometer - credits : BNF