Abstract: A polychromatic mutual alignment device for an aiming apparatus includes an optical mixer having at least two holes each receiving light emitted in one of different spectral ranges for which boresighting is to be achieved and a plate which is transparent in a wave length range and reflective in another wave range for combining the two light beams into a common block output beam. A parabola mirror receives the output beam at an angle with respect to its axis. The mixer and the mirror being so located that all source-forming holes are at the focus of the mirror.