A viewer for viewing an object under magnification, the viewer comprising: an objective lens for producing an image of an object located at an object plane and having a radial extent defined by an aperture stop; a partially-transmissive reflector for allowing transmission of light therethrough from the objective lens to a mirror arrangement and providing for reflection of light which is returned thereto from the mirror arrangement; a mirror arrangement which receives a light component from the partially-transmissive reflector, and is located such that a focussed image of the object is produced at the mirror arrangement and light received by the mirror arrangement is reflected back to the partially-transmissive reflector and relayed to produce an image of the object; and a viewing lens arrangement for producing an optical image of the object which is viewable by an observer at an exit pupil at a viewing plane; characterized in that: the objective lens has a beam path angle (α) which is an angle subtended from a point where an optical axis of the objective lens meets the object plane and defined by a distance along the optical axis from the object plane to the objective lens and the radial extent of the aperture stop; the viewer has a maximum viewing angle (β) which is an angle subtended from a point on the mirror arrangement at an optical axis of the mirror arrangement and defined by a distance along the optical axis from the mirror arrangement to the viewing plane and a radial extent of the exit pupil at the viewing plane; and the viewer is configured such that a displacement ratio of the beam path angle (α) to the maximum viewing angle (β) is at least 3:1. an objective lens for producing an image of an object located at an object plane and having a radial extent defined by an aperture stop; a partially-transmissive reflector for allowing transmission of light therethrough from the objective lens to a mirror arrangement and providing for reflection of light which is returned thereto from the mirror arrangement; a mirror arrangement which receives a light component from the partially-transmissive reflector, and is located such that a focussed image of the object is produced at the mirror arrangement and light received by the mirror arrangement is reflected back to the partially-transmissive reflector and relayed to produce an image of the object; and a viewing lens arrangement for producing an optical image of the object which is viewable by an observer at an exit pupil at a viewing plane; characterized in that: the objective lens has a beam path angle (α) which is an angle subtended from a point where an optical axis of the objective lens meets the object plane and defined by a distance along the optical axis from the object plane to the objective lens and the radial extent of the aperture stop; the viewer has a maximum viewing angle (β) which is an angle subtended from a point on the mirror arrangement at an optical axis of the mirror arrangement and defined by a distance along the optical axis from the mirror arrangement to the viewing plane and a radial extent of the exit pupil at the viewing plane; and the viewer is configured such that a displacement ratio of the beam path angle (α) to the maximum viewing angle (β) is at least 3:1. the objective lens has a beam path angle (α) which is an angle subtended from a point where an optical axis of the objective lens meets the object plane and defined by a distance along the optical axis from the object plane to the objective lens and the radial extent of the aperture stop; the viewer has a maximum viewing angle (β) which is an angle subtended from a point on the mirror arrangement at an optical axis of the mirror arrangement and defined by a distance along the optical axis from the mirror arrangement to the viewing plane and a radial extent of the exit pupil at the viewing plane; and the viewer is configured such that a displacement ratio of the beam path angle (α) to the maximum viewing angle (β) is at least 3:1.