I am sitting watching on SciHD channels broadcast of the Moon Machines - Navigation Computer video. You can watch the video here on Youtube.
Here is more about the Navigation System. We take for granted knowing your location. Location is an immutable fact except when you can't figure out where you are. It's called being lost.
Sextant, Apollo Guidance and Navigation System
Date manufactured: 1960's, Kollsman Instrument Company
Description: Between December 1968 and December 1972, a total of nine Apollo spacecraft carried human crews away from the Earth to another heavenly body. Primary navigation for these missions was done from the ground. As a backup, and for segments of the mission where ground tracking was not practical, an on-board inertial navigation system was used. Astronauts periodically used a sextant to sight on stars and the horizons of the Earth and Moon to align the inertial system, and to verify the accuracy of the Earth-based tracking data.