In April 1970, the crew of Apollo 13 navigated home by holding the spacecraft against the terminator of the Earth, the line where day met night on the planet they were trying to reach, timing a fourteen-second engine burn with a wristwatch because their guidance computer had been shut down to save battery power for reentry

With the Apollo Guidance Computer shut down to save battery power for reentry, the crew of Apollo 13 navigated home by holding the lunar terminator in a window crosshair and timing engine burns with an Omega Speedmaster wristwatch. The post In April 1970, the crew of Apollo 13 navigated home by holding the spacecraft against the terminator of the Earth, the line where day met night on the planet they were trying to reach, timing a fourteen-second engine burn with a wristwatch because their guida