Abstract: A compact, all-reflecting optical system for viewing distant objects. The system comprises a negative convex secondary mirror placed between a positive concave primary mirror and a positive concave tertiary mirror. The system has an eccentric field of view in that the field of view lies entirely on one side of the optical axis, and because of this, the light travelling from the object to the image will pass entirely outside the secondary mirror, both when entering the system and when travelling from the tertiary mirror to the image. Accordingly, with the present invention, there is no central obstruction and no consequent restriction on field of view and power distribution between mirrors as is found in prior art all-reflecting systems.