The potential of Meudon spectroheliograph for investigating long term solar activity and variability

Observations of the chromosphere with Deslandres’s spectroheliograph started at Paris Observatory in 1893 and were followed by systematic observations Meudon since 1908. The solar collection Hα CaII K images is probably longest available worldwide, associated products such as synoptic maps tables. Since 2018, only instrument producing data-cubes full line profiles H, Hα, for each pixel disk. Slices cubes provide monochromatic images. We summarize this paper capabilities successive generations instrument, explore potential analysis rare events, investigations past activity studies long term variability.