  We propose a form of a lens corrector at the prime focus of a hyperboloidal
mirror that provides a flat field of view up to 3 deg diameter at image quality
D_{80} < 0.8 arcsec in integrated (0.32-1.10 mcm) light. The corrector consists
of five lenses made of fused silica. Only spherical surfaces are used, so the
system is capable of achieving better images, if necessary, by aspherizing the
surfaces. The optical system of the corrector is stable in the sense that its
principal features are retained when optimized after significant perturbations
of its parameters. As an example, three versions of the corrector are designed
for the V.M.Blanco 4-m telescope at Cerro Tololo Inter-American Observatory
with 2.12 deg, 2.4 deg, and 3.0 deg fields of view.
