  We develop a methodology that enables us to extract accurately the
electromagnetic Delta form factors and their momentum dependence. We test our
approach in the quenched approximation as a preparation for a study using
dynamical fermions. Our calculation of the four form factors covers pion masses
between about 410 MeV and 560 MeV on lattices with a size of 2.9 fm and a
lattice spacing 0.09 fm. From the form factors we are able to obtain estimates
of the magnetic moment and the charge radius of the Delta, which we compare to
existing experimental and theoretical results.Our non-zero result for the
electric quadrupole form factor signals a deformation of the Delta, pointing to
an oblate charge distribution.
