An all-reflective optical system includes a primary mirror of ellipsoidal configuration, a secondary mirror of hyperboloidal configuration facing the primary mirror, and an eye-piece that includes: a positive-powered tertiary mirror having a majority of positive power that is expected in the eye-piece and configured to substantially collimate light rays incident thereon; and a negative-powered near-flat quaternary mirror having lesser power than the tertiary mirror and configured to receive the substantially collimated light rays from the tertiary mirror, further collimate the received light rays and reflect the further collimated light rays to an exit pupil. The primary mirror, the secondary mirror and the eye-piece thereby form an afocal optical system.