Abstract: An optical observation device for observing a target located at a distant observation sight that comprises an observation telescope and an infrared sighting device. The infrared sighting device eventually provides a visual target image as a sighting marker from a thermal infrared image of the observation sight. The sighting marker and the observation sight are simultaneously viewed in the field of view of the observation telescope so as to enable training of the observation telescope on a part of the observation sight where the target is located.