The Dambusters raid

617 Squadron flew the dams raid at sixty feet in the dark, on a date chosen for moonlight and water level.

The bouncing bomb had to be released at exactly 60 feet and 232 mph, at night, over water, and a 91% moon was the only thing making the surface visible. Two spotlights angled to converge at 60 feet solved the height problem; the Moon had to solve the rest.