  The main characteristics of a wide photometric survey of the Sgr dwarf
spheroidal galaxy are shortly presented. V and I photometry has been obtained
for ~ 90000 stars toward Sgr and for ~ 9000 stars in a region devoid of Sgr
stars (for decontamination purposes). The full potential of this large database
is far from being completely explored. Here we present only preliminary results
from the analysis of statistically decontaminated Color Magnitude Diagrams,
trying to set a scheme of the Star Formation History of the Sgr Galaxy. A
scenario is proposed in which star formation in Sgr began very early and lasted
for several Gyr with progressive chemical enrichment of the Inter Stellar
Medium (ISM). Nearly 8 Gyr ago the star formation rate abruptly decreased,
perhaps in coincidence with the event that led to the gas depletion of the
galaxy. A very small rate of star formation continued until relatively recent
times (~ 1 Gyr ago).

Astrophysics