Abstract: Off-axis guiding apparatus for a reflecting telescope having a main focusing tube transverse to the telescope barrel and light deflecting means in the barrel reflecting light into the main focusing tube comprises a turntable mounted to straddle the telescope barrel and supporting the main focusing tube, rotatable about the axis of that tube, and also supporting an auxiliary focusing tube having its lower end adjoining the lower end of the main focusing tube, but its axis inclined to the axis of the main focusing tube, and light deflecting means adjustably affixed to the turntable so as to deflect peripheral light from that reaching the main focusing tube into the auxiliary focusing tube.