Celestial navigation isn't difficult. I learned the basics in an afternoon. It requires a sextant, a calculation book, and a really good timepiece. If you've noticed that really expensive watches have a maritime theme it's because accuracy costs money in an era before NTP servers and GPS.

In a small sailboat rocking in 3-4 foot waves I was accurate to ~50 miles. The crew member who taught me was accurate within a mile. He was also 65 and felt the GPS was almost as accurate as his sightings :-)