One of us (E. Nesme) is grateful to the Ministery of Defense, for encouraging and funding the long-term spectroheliogram research program, through military contracts (no. 010481/ETCA, no. 012736/DRET-ETCA, and no. 92-2011.A/DRET-ETCA). The extensive work of the spectroheliogram observations team has been crucial for almost a century. We thank the present team for maintaining and improving the observational program over the years. Spectroheliograms were digitized with the Machine à Mesurer pour l'Astronomie (MAMA) of the Institut National des Sciences de l'Univers, at the Paris Observatory. Our thanks also go to P. Micheneau, R. Chesnel, and P. Toupet for their assistance in the data acquisition.
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998