An observation instrument has a hollow shaft in whose distal end region there is arranged an optoelectronic imaging system which has on the image entrance side a distal deflection prism whose deflection faces lead an image into an optical lens system which images the image onto the image plane of an image sensor arranged proximally from the lens system, the image sensor having an active region which is situated asymmetrically relative to the outer contour of the image sensor. A first plane, which is defined by the main beam and a first orthogonal on the image plane of the image sensor, and a second plane, which is defined by the main beam and a second orthogonal on the deflection faces of the distal deflection prism, being rotated relative to one another about the main beam in such a way that it is possible to produce a sight cone which is symmetrical relative to a midplane of the hollow shaft and whose image area is situated fully in the active region of the image sensor.
