NavList:

Hello Huub,

Thank you for your comments.

My unit is designed to run completely independent of the boat. If it is kept disconnected and stored in a metal box, I hope it would survive even a serious lightning event.

The unit contains everything needed for backup celestial navigation: an accurate UTC clock, the Nautical Almanac, and the sight-reduction data, all stored inside the unit. So in principle, no paper almanac or sight-reduction tables are needed.

But yes, you still need a sextant, and you still need to know how to use it. The idea is that you take the sights, enter the sextant readings into the module, and after a few observations the unit can calculate a position for you.
It can also suggest which celestial bodies are worth observing at the current time and position estimate.

For many sailors, a spreadsheet calculator, a normal calculator, or doing the work fully by hand may be the better solution. Many already do that very well.

My intention is simply to use knowledge I already have, especially microcontrollers and programming, to build myself a helper that may be useful one day. It does not cost too much, and like much safety equipment on a boat, I hope it isnever really needed. I will probably also use it underway just for practice and fun.

For the battery, yes, batteries are always a concern. My unit uses a 6Ah LiFePO4 battery, and when it is powered off it draws about 0.0001A. In theory, that means the battery should last for many months.

Even so, the best routine is to take the unit out of the box now and then, connect the charging cable to normal 12V onboard power, and power it up. That way the UTC clock can be disciplined and checked, and the battery can be safely recharged.

But again, there is no magic here. A calculator, the Nautical Almanac, and the sight reduction tables can do the same job if you have enough practice and experience to do it manually.

Regards Knut