Celestial Navigation? Forget it!
Even though I have a very nice GPS, I still dust off the ole sextant once a month. I do it mostly for mental exersice, but it''s nice to know that in a pinch I could still find my way around.
BTW, the military still controls the signals sent by all navigational satilites. In an emergency situation, they can render all non-military GPS systems completely useless.
Murphy may not need to get on board, he can be thrust upon you. As far as I know, the military has not yet figured out how to control the Sun, Moon, and Stars. ;^)
~ Happy sails to you ~