Optical instrument and method for optical monitoring the surroundings of slowly moving vehicles

The optical instrument has observation lens (2) that is arranged on symmetry axis at preset distance from overview lens, and whose optical axis is perpendicular to symmetry axis of overview lens. A control unit (4) actuates the observation lens. An imaging optical system acquires the observation image and overview image of surroundings of environment by observation lens and overview lens. An evaluation unit (5) evaluates the observation image and overview image based on distance between observation lens and overview lens. Independent claims are included for the following: (1) agricultural vehicle; and (2) method for monitoring environment of vehicle.