Abstract. In this paper, all the light-curves obtained during the PHEMU91 campaign of observations of the mutual phenomena of the Galilean satellites are presented. These observations give accurate astrometric positions of major interest for dynamical studies of the motion of the Galilean satellites. The aim of this work is to give observational data directly usable for theoretical studies. We made 374 observations of 111 mutual events from 56 sites. The corresponding data are given in this paper 1 . The accuracy of each observation has been deduced from a comparison with the theoretical predictions. For each observation, information is given about the telescope, the receptor, the site and the observational conditions.Send offprint requests to: J.-E. Arlot

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Linear optical polarization of 88 Her has been measured in V spectral region during the period 1974–1985. The mean annual values of the intrinsic polarization parameters are presented. The polarization percentage changes from 0.15%(1976) to 0.56%(1979). Small values of the polarization percentage correspond to the period when the envelope effect is negligible. The maximum of polarization percentage has been found during the early period of strong shell phase. The polarization position angle varies between 53 and 83 degrees.

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Here we have juxtaposed two distant cosmic locations of the Sun and AGN where neutral hydrogen appears in a close connection with hot coronas. Besides the solar photosphere, chromosphere and prominences where the presence of neutral hydrogen is well established, its emission quite high in hot solar corona is still puzzling. Some of earlier observations where H? emission in solar corona was detected in eclipse and in daily coronagraphic observations are reviewed. A proper theoretical explanation of this cold chromospheric-type emission in the hot corona does not exist yet. On the other side, a similar emission of hydrogen lines is present in Active Galactic Nuclei (AGNs). Much research work is currently being done in this field. We outline some of the concepts of the AGN structure prevailing in the astrophysics today.