Navigation has been a "collateral" duty for an officer in the navy for at least the last thirty years. That's hardly a condemnation of celestial navigation-more an indictment of the navy. Where's Harry Weems when you need him? Two mile accuracy is adequate for any off-shore navigation system and, in fact, that is the standard. If you need greater accuracy you are probably in a piloting situation. And I would not classify two miles as a good observation in good conditions. With a cheap sextant or poor conditions, ie... rolling deck underfoot, not bad, but I wouldn't consider it my best effort. Refraction is a zero sum game with a marine sextant as horizon and sky glass experience the same and cancell. A bubble sextant is different and those correction factors are included in the air navigation tables. The colregs require decision-making not be done based on scanty information, especially scanty radar information. I,m sure that you've heard of radar assisted collisions. The important point being that the prudent navigator is required to utilize all means of navigation (that's why the radar is on even in perfect visibility) and you do not know there is an error in an electronic instrument unless you compare it to some other reference. All of the maritime academies still teach celestial navigation and the USCG still tests it for licensing (90% is passing grade) and that's why shipowners entrust 150 million dollar ships to them. Use every tool you have, but don't tell me that GPS has eliminated the need for celestial navigation. But then, some people don't see the need for paper charts either!