I've written before about the decreasing practical utility of Celnav:http://cpyoa.geekworkshosting.com/forum/index.php?topic=7942.0
But I do find myself disagreeing with some of your comments about the "app". Why bother having an app and a link to yet another device and the Web when you can simply get a cheap and robust hand-held GPS as a backup? The whole idea is to make yourself less
dependent on electronics, not simply substituting one more delicate device and corporate/government bureaucratic infrastructure for another. Besides, learning modern technology is not only a colossal PITA, but they keep on changing it on you so you have to buy into some other "improvement". And by "buy" I mean spending more ca$h, as well as the investment in mastering yet another piece of software. I don't know about you, but I'm getting too old to waste my remaining hours learning anything with a limited shelf-life.
If you're seriously considering Celnav as a backup to electronics, but don't want to get bogged down in the heavy expense, training, drill and practice involved, your best bet is to split the difference. Get a cheap plastic sextant, and reduce your sights with a pocket calculator instead of cumbersome sight reduction tables. The calculator can be solar-powered, and very compact and rugged, and costs only about $20. You can even afford buying a couple! One of the chapters in my course is devoted to calculator sight reductions. It is easier than learning a new user interface, believe me.http://cpyoa.geekworkshosting.com/forum/index.php?topic=3641.0
And if you forget how to do it in a time of emergency, it can be quickly looked up in page 279 of the Nautical Almanac.
Of course, you'll still have to learn how to handle the sextant and use the Nautical Almanac to get the astronomical data; but like sight reduction tables, this requires no advanced skills in spherical trigonometry or nautical astronomy. All you really need to know is how to add up columns of figures. The modern procedures for celestial navigation have been designed so that any mariner can learn them.The skills you need for celestial navigation are the same ones you already need as an offshore sailor: piloting, dead reckoning, plotting, coordinate systems, chartwork, timekeeping, and a basic understanding of the calendar. If you've substituted electronics for those, you're already in trouble.
The major advantage of Celnav is that it is where all the navigational arts intersect, where it all comes together. When you understand it, you understand the relationship of your boat to the sky, and to the sea. And your understanding is complete. If your clocks fail, or your Almanacs expire, or you drop your sextant over the side, you can still do something
, you can still navigate at some simpler level, as did our ancestors. The skills and knowledge you have to master to do Celnav are valuable skills, they will always be there and they will always be useful, even if all the books and gadgets needed to navigate by the stars are lost. When you press a button on your electronics and nothing happens, you have absolutely nothing to fall back on.
Don't get me wrong. Going offshore without all the tech you can afford is downright irresponsible. We have these conveniences, and they can be life-savers. We should certainly take advantage of them; never go into the woods without a compass, knife and matches. But you'll never regret having learned how to build a fire from scratch.