NavList:

Robert,

Yes, you are probably right about the cast of hundreds probably required to support our "self contained" back up hobby. I guess this compares with the cast of thousands behind GPS.

At absolute basics, what about a home made sextant (easy enough to do, see books by Tony Crowley, or Denis Fisher), a home made nocturnal (even easier, see same books). Only "almanac data" required 1) kowledge of current polaris declination and ability to edit this over the years, 2) tables of sun declination and equation of time (easy enough to self generate.) I can now find latitude with reasonable accuracy. No cast of hundreds required  for latitude.

For longitude, please let me have my mechanical watch and let me know the longitude of my garden,( previously prepared by carefully pacing out the distance from there to Greenwich !) I can now  check and correct the  watch by measuring LAN. Now I can find longitude.

I grant you, I cannot make a watch, but I suspect there would be a watchmaker craftsman within a hundred miles who could (probably be very expensive and take years to build though!).

For the "full Monty" as we say in England, I guess we could generate our own almanac data with a computer, but then we are back to the slavery of the cast of thousands for that marvel of human achievement.

Fundamentally though, no man is an island and we have always done best in  cooperative teams. The original Nautical almanac from the Royal Observatory in Greenwich probably required a cast of dozens, not hundreds. A similar small team of astronomers and mathematicians could probably produce an NA today. However, the fully "self contained " cel nav person would be a sorry fellow all on his own, knowing where he was, but no-one else to share that knowledge with.

All good fun though.

Francis