70 years of spectroscopy of the photosphere and the solar chromosphere at the Pic du Midi Observatory (1956-2026)

TL;DR

This paper reviews 70 years of solar spectroscopy at Pic du Midi Observatory, highlighting technological developments, infrastructure evolution, and scientific contributions to understanding the solar photosphere and chromosphere.

Contribution

It provides a comprehensive historical overview of instrumentation and observational progress in solar spectroscopy at Pic du Midi from 1956 to 2026.

Findings

Development of specialized spectrographs and domes over decades.

Evolution of infrastructure supporting solar observations.

Key scientific insights gained from long-term solar spectroscopy data.

Abstract

Observations of the solar corona at the Pic du Midi began with Bernard Lyot and his spectro coronagraph installed on the multi-purpose equatorial mount of the Baillaud cupola. It was not until 1956 that domes and instruments specifically dedicated to observations of the photosphere and the solar chromosphere appeared. On the occasion of the International Geophysical Year, a solar spectroscopy laboratory was created to the west of the Pic du Midi, based on two spectrographs of 4 m and 9 m focal length. In 1961 the turret dome appeared to the east of the Pic, later equipped with an 8 m spectrograph. Around 1965, the Baillaud dome finally specialized in the corona with a new table and new spectrographs. At the same time, a revolution in infrastructure took place at the Pic in a few years, which we present as well as the solar spectrographs and their goal.