Guy Ratier
The Pic-du-Midi, on the French side of the Pyrénées, became a state observatory in the summer of 1882. The first major astronomical event to be observed was the Venus transit of 6 December 1882. Unfortunately this attempt by the well-known Henry brothers was unsuccessful due to bad weather conditions.
During the twentieth century, the Pic-du-Midi became famous for the quality of its solar and planetary observations. In the sixties, Jean Rösch decided to use this experience to monitor the transits of Mercury. The objective was not to measure the parallax, but to determine the diameter of the planet in order to confirm its high density. Observations were made using a photometric method - the Hertzsprung method - during the transits of 1960, 1970 and 1973.
The pioneer work of Ch. Boyer on the rotation of the Venus atmosphere as well as some experiments involving Lyot coronographs are also noteworthy.
A Venus transit was finally observed on 8 June 2004 with a new CCD camera, providing a significant contribution to the model of the Venus mesosphere. This opened the field for new observations in 2012.
Manuscript: jad19_1r.pdf