A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Jeremy C
Date: 2018 Sep 25, 04:39 -0700
I'm a bit turned around by what you're asking for. Are you looking for a timepiece independent of GPS to keep accurate time without an outside reference? Even if HF and GNSS fail for some reason, the atomic clock time standards should be readily available via the internet. You might only get concerned if you were away from such a reference for a long period of time, say a slow ocean passage of many weeks. In that case, if you don't trust GNSS time, you'd need a chronometer. The key with the chronometer isn't how absolutely accurate it is, it is that it has a constant error rate. Most time pieces fail this test. If you know that it takes a week for the clock to gain a second, you can project what time it is for any amount of time after your last reference. For example, 4 weeks later, you will be 4 seconds fast. The absolute accuracy of the clock isn't good, but you know how to correct it.
Quartz chronometers aren't hugely expensive, but you do need to determine the error rate before you can work with them effectively. Watches are hit or miss, but I've had $30 Timex Ironmen watches that didn't change over a second in a month and I've seen expensive rolexes that don't keep time well at all.
Many people don't want WWV to go away more so that it's a very good radio frequency reference as much as a time reference.
I don't know how far out to sea you expect to go, but most modern watches will keep sufficiently accurate time for most cruises. Even if you're a second or two off, it won't affect your celnav enough to miss landfall.