Abstract: An optical sighting device consists of a hood with two windows which can transmit radiation within predetermined wavelength ranges to a rotatable reflecting device. The reflecting device receives radiation from one or other of the windows and the hood is rotatable subject to the rotation of the reflecting device. The radiation reflected by the reflecting device is received by two dichroic mirror plates which are suitable for transmitting or reflecting thermal infra-red radiation, visible radiation and near infra-red radiation towards suitable corresponding detectors.