  Systematic observations of the chromosphere and the photosphere started in
Meudon Observatory 115 years ago with Deslandres spectroheliograph. An
exceptional collection of more than 100 000 monochromatic images in CaII K and
H$\alpha$ spanning more than 10 solar cycles is proposed to the international
community by the BASS2000 solar database. We started in 2023 a ''PRO-AM''
collaboration between professional and amateur astronomers with the Solar
Explorer (SOLEX), a compact and high quality spectroheliograph designed by
Christian Buil, in order to record images every day, and several times per day,
owing to tens of observing stations in various places. This paper summarizes
the scientific objectives and provides practical and technical information to
amateurs willing to join the observing network.
