Mean value of the solar radius obtained at the Cote d'Azur Observatory (Solar Astrolabe of Calern Site, 1975-1998)

We propose a mean value for the solar radius based on by a program of visual observations and CCD measurements carried out at the Cote d'Azur Observatory between 1975 and 1998. The working assumption is that there are no variations in the semi-diameter. Over a set of more than 8 000 observations, the mean value amounts to 959.51 +/- 0.01 " for a solar radius seen from a distance of 1 astronomical unit. As visual and CCD series are closely linked, the coherence of the results calls for some qualification of visual observations. Apparent variations of the solar radius recorded over more than 20 years will be addressed in a future note. (C) Academie des sciences/Elsevier, Paris.