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Coronagraphy

It is the study of the solar crown (corona) which is the "atmosphere" of the Sun, constituted of a gas which is little dense and very warm (up to 2 million degrees). This observation is difficult due to its luminosity being 1 million times weaker than that of the "surface" of the Sun, the photosphere. Therefore the light is completely flooded in the light which we receive.
A total Sun eclipse is the only natural event, which combines the conditions to be able to observe it. But this is a rare phenomenon, which is of short duration (maximum 7.30 minutes).
Therefore, specialists use a coronagraph, an invention by a French astronomer Bernard Lyot. It is an instrument (lens) which artificially reproduces an eclipse of the Sun.

The understanding of the internal functioning of the Sun is based on indirect observations, in particular, by the study of the solar corona and a few of its characteristics (temperature, magnetism, density).

Coronagraphy at Pic du Midi

For more than 70 years, due to the excellent conditions which the site has, the Pic du Midi, is an active site in the coronagraphic field, in particular, in the study of the dynamic phenomena.

At an altitude of 2860 m the atmospheric pressure is 1/3 less dense than in the plain. There are fewer clouds and less pollution. The altitude is favourable for the study of the solar corona.