  The manuscript New Theory of Sunspots was identified and attributed to the
Jesuit astronomer and hydrographer from Marseille Esprit Pezenas (1692-1776)
during the year 2002, during the systematic search for papers concerning him in
the various French funds. The manuscript, in large part unpublished, New Theory
of Sunspots was written by astronomer and professor of Marseilles Jesuit
hydrography, Father Esprit Pezenas (1692-1776). The text was composed and
revised between the years 1766 and 1772. In this manuscript, of which we are
going to study the conditions of its composition, P. Pezenas gives one of the
last geometric methods, related graphical methods, allowing the inclination of
the Sun's equator to be deduced on ecliptic, using three observations of a
sunspot, at given times, and in taking into account the movement of the Earth
with respect to the Sun during the duration of observations. This text contains
all the digital elements allowing to follow and understand the application of
geometric processing methods of observations and observation techniques
mentioned above in the introduction: passages of edges and Sun spots at the
meridian, use of objective micrometers and wire micrometers. At detour of his
calculations, Father Pezenas announces a duration of about 26 days and 9 hours
for the rotation of the Sun around its axis, comments on and corrects some
observation data published in Le Monnier's Heavenly History.
