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

I have to admit that I continue to remain a little surprised that the Apollo 13 astronauts made it home it all. 

But then that’s the human spirit in a nutshell. They used their intuition, communication with the ground, and fought hard to keep “luck” on their side. 

 

https://spacedaily.com/sd-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-fou/