rear view of the sight bm-21 grad, 9k51. multiple launch rocket system of 122 mm caliber. a device for navigating the coordinates

rear view sight bm21 grad 9k51 multiple launch rocket system caliber 122 device mechanism guidance artillery mount tubular rails while rotating squeeze handle coordinates launcher grau 2b5 fire control battery rotation twist numbers direct vertical plane horizontal horizon aiming accurate accuracy target analysis objective circle detailed eyes vision glasses front vizier diopter direction bm-21 9k51 caliber for navigating installation from four rows