Bernard Lyot invented the monochromatic birefringent filter in 1933 in order to investigate the coronal emissions of solar structures above the limb with the coronagraph installed at the Pic du Midi observatory. The filter was improved later and he made the first observations of the chromosphere above the solar disk in 1948, at Meudon. After his death, Grenat and Laborde continued the development in the frame of the coming International Geophysical Year (IGY 1957-1958). A modern Hα heliograph was completed soon and the flare patrol started in 1956. This instrument was reproduced by two companies (SECASI and OPL) and disseminated around the world in order to contribute to the IGY common effort dedicated to the solar activity survey. We describe in this short paper the capabilities of one of these copies operating at Haute Provence station from 1958 to 1994.