Celestial Navigation? Forget it!
Total electrical failures possible? Even with 9+ levels of electrical redundancy aboard modern day aircraft and their magical glass cockpits you still find a needle, ball and airspeed. Wonder if the engineers were thinking that they''d just throw them in for nostalgia''s sake or they thought that maybe there was a possibility that electricity really could fail - totally. If you''re gonna take your frail human body into areas where survival depends upon your skill at using what''s at hand I think it would be prudent to back yourself up by having as many things ''at hand'' as you feel you have the skill to use. If not a sextant there are other "back-ups" as mentioned in previous posts that will help keep you a self-sufficient and safe seaman.