This circuit generates bright, short flashing pulses that are visible even from a distance. LEDs can withstand such short pulses (30-40 ms) with approx. 50 mA without any problems if they are repeated only every 0.5 - 1 s. This makes the flashes clearly visible from a long distance. Super-bright LEDs in a transparent housing are the best choice.

Construction by Nico from Flensburg:

Literature: Schreiber - 50 Hobby Schaltungen mit Leuchtdioden, Franzis Verlag 1982