An optical device includes an objective, an eyepiece and a power corrector, each of which includes one or more lenses, and each of which has a respective focal length. The input focal length of the device is defined jointly by the focal lengths of the objective and the power corrector. The magnification of the device is the ratio of the input focal length to the eyepiece focal length. The combined aberration of the eyepiece and the power corrector is less than the characteristic aberration of the eyepiece. The objective, the eyepiece and the power corrector together define an apparent field of view of at least 75 degrees and an exit pupil. The eyepiece lens diameter(s) is/are no greater than twelve times the pupil diameter and three times the eyepiece focal length.