Abstract: An astronomical viewing instrument with a helmet-mounted optical assembly comprising a pair of binocular tubes, each with an objective lens, attached to a base plate. The base plate is connected via a first hinge to the helmet worn by the viewer. The binocular tubes are also attached to a first pair of apertures in a mirror housing which has a second pair of apertures with threaded tees, at an angle relative to the first pair, for connection to a pair of prism housings ending in eyepieces for the viewer. The prism housings provide for a parallel offset such that their individual rotation around the mirror housing tees changes the distance between the eyepieces to match the distance between the pupils of the viewer. The first hinge serves to accommodate different head sizes of viewers and allows to adjust the weight, via the cushioned eye-pieces, on the eyes of a viewer.