But they are plain as day on a clear night. BTW, in my day lots of USAF people seemed to be lost, so I must take the word of a USAF Navigator cum grano salis, economy size.
Old dogs, new tricks ....
Galileo’s proposal — Jovian moons
In 1612, having determined the orbital periods of Jupiter’s four brightest satellites (Io, Europa, Ganymede and Callisto), Galileo proposed that with sufficiently accurate knowledge of their orbits one could use their positions as a universal clock, which would make possible the determination of longitude. He worked on this problem from time to time during the remainder of his life.
To be successful, this method required the observation of the moons from the deck of a moving ship. To this end, Galileo proposed the celatone, a device in the form of a helmet with a telescope mounted so as to accommodate the motion of the observer on the ship.[6] This was later replaced with the idea of a pair of nested hemispheric shells separated by a bath of oil. This would provide a platform that would allow the observer to remain stationary as the ship rolled beneath him, in the manner of a gimballed platform. To provide for the determination of time from the observed moons’ positions, a Jovilabe was offered — this was an analogue computer that calculated time from the positions and that got its name from its similarities to an astrolabe.[7] The practical problems were severe and the method was never used at sea. However, it was used for longitude determination on land.
But I was never lost with my sextant, a good compass, and a good time hack.