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Henri Deslandres initiated imaging spectroscopy of the solar atmosphere in1892 at Paris observatory. He invented, concurrently with George Hale inKenwood (USA) but quite independently, the spectroheliograph designed formonochromatic imagery of the Sun. Deslandres developed two kinds ofspectrographs: the ''spectroh{\'e}liographe des formes'', i.e. the narrowbandpass instrument to reveal chromospheric structures (such as filaments,prominences, plages and active regions); and the ''spectroh{\'e}liographe desvitesses'', i.e. the ''section'' spectroheliograph to record line profiles ofcross sections of the Sun, in order to measure the Dopplershifts of dynamicfeatures. Deslandres moved to Meudon in 1898 with his instruments and improvedthe spectral and spatial resolutions, leading to the large quadruplespectroheliograph in 1908 developed with Lucien d'Azambuja. CaII K systematicobservations started at this date and were followed in 1909 by H$\alpha$ withtwo dedicated 3-metres spectroheliographs. The observing service was organizedby d'Azambuja who also intensively used the large 7-metres spectroheliographfor his research and thesis (1930). This paper summarizes fifty years ofresearch by Mr and Mrs d'Azambuja, who explored various photospheric andchromospheric lines, performing special spectroheliograms with the highdispersion 7-metres instrument. They also observed intensively filaments andprominences (memoir published in 1948) and recorded rare solar activity eventswith the two 3-metres spectroheliographs, during the first half of thetwentieth century.

Special spectroscopic observations and rare solar events collected in the first half of the twentieth century with Meudon spectroheliograph