Louis Thollon (2 May 1829 – 8 April 1887) was a French astronomer.
He was born in Ambronay, France.[1] Beginning in 1881, Thollon joined the staff of the new Nice Observatory where he undertook a long-term observation program of the Sun using a spectroscope of his own design.[2] In the process, he recorded a solar spectrum consisting of 3,000 absorption lines in the optical band.[3]
In 1882, he joined André Puiseux on an expedition to Egypt to observe the solar eclipse on 17 May.[4] The same year he traveled to Portugal to watch the Venus transit, but was met with disappointment due to poor weather.[5] He was awarded the Prix Lalande in 1885 for his large map of the solar system, which was not published until after his death in 1890.[6] During the 1886 Mars opposition, he assisted the observatory director, Henri Perrotin, in observing the planet with a 15 in (38 cm) reflecting telescope. Both men reported that they spotted canali on the surface of the planet, apparently confirming the 1877 discovery of these features by Italian astronomer Giovanni Schiaparelli.[7] Thollon died at age 57 in Lyon, France.[1]