Abstract: An optical system including at least one lens and erecting mirrors designed and arranged to give an inherent aperture and field greater in one direction than another direction. By using a low power eyepiece lens it is possible to arrange for a user's eye or eyes to be further behind the eyepiece lens so that the user can wear normal spectacles to correct for eye defects. When a pair of the optical systems is used in a pair of binoculars, it is possible for the exit pupils to be in a form of horizontal slots so the systems do not have to have adjustable spacing to allow for a particular user's eye separation.