[throw0101d]

> Are there any available clocks with that precision?

Citizens says ±1s/year with their Caliber 0100:

* https://www.citizenwatch-global.com/the-citizen/lineup/cal01...

* https://www.hodinkee.com/articles/citizen-eco-drive-caliber-...

Solar powered as well.

It should be noted that Harrison's watches were low-volume productions, so could be tuned very accurately—and their accuracy was a matter of life and death for ships and their crew. Most mechanical watches 'normal' people can get nowadays are produced at much higher volumes, and so aren't adjusted as much—especially since few people demand it and are willing to pay for it:

* https://www.hodinkee.com/articles/how-accurate-should-your-m...

The Harrison watches/clocks were built for the British government/Navy, so were fairly price insensitive (military procurement and such).

Being 1 minute off in time throws off distance by 15 nautical miles (~28 km), so being off by a second can cause about 500m worth of position inaccuracy.

Also: it may not be a big deal if your clock/watch drifts as long as it does so at a known, consistent rate which you can adjust for.

[SoftTalker]

> Being 1 minute off in time throws off distance by 15 nautical miles

I'm surprised that the accuracy of a hand-held sextant used while standing on a rolling/pitching deck is good enough for that to matter very much.

[storyinmemo]

> Modern sextants can read the angle to a 0.1 minute level of accuracy, i.e. one-600th of a degree or one-tenth of a mile. In practice, actual accuracy to one-half mile is acceptable and quite good. The usual standard is accuracy to within five miles. The sextant (or octant) is meant to get the ship across the ocean. Once near the coast (20-100 miles) the more accurate techniques of piloting are relied upon for a safe landfall. The sextant is still the standard instrument for taking the observations required for celestial navigation.

https://www.ion.org/Museum/item_view.cfm?cid=2&scid=14&iid=2...

One thing that helps with a pitching deck is that the horizon and object remain the same angle. Like a camera following race car, the objects move together.

[throw0101d]

> […] for that to matter very much.

Life and death at times:

> The Scilly naval disaster of 1707 was the loss of four warships of a Royal Navy fleet off the Isles of Scilly in severe weather on 22 October 1707.[a] Between 1,400 and 2,000 sailors lost their lives aboard the wrecked vessels, making the incident one of the worst maritime disasters in British naval history.[2] The disaster has been attributed to a combination of factors, including the navigators' inability to accurately calculate their positions, errors in the available charts and pilot books, and inadequate compasses.[3]

* https://en.wikipedia.org/wiki/Scilly_naval_disaster_of_1707

When you're trying to find a tiny speck of an island (Pitcairn, Saint Helena, etc) in the middle of an ocean it's also important.

[SoftTalker]

Yeah I get that it's important, I just didn't realize that angles could be meaured so accurately by eye at that time (especially on a ship that's moving around on even a moderate sea).

[throw0101c]

> I just didn't realize that angles could be meaured so accurately by eye at that time

Sextants have a bit of magnification (usually 4x, but sometimes 7x or higher). Higher mag allows for better accuracy at the cost of more shaking of the view.

Basic explanation:

* https://www.youtube.com/watch?v=30_wEda3ltM

[dredmorbius]

It was good enough for the Boeing 747:

<https://virginflightdeck.blogspot.com/2010_09_01_archive.htm...>

(Something of a stealth favourite amongst HN commenters: <https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...>)

And not the only plane to make use of this option: <https://news.ycombinator.com/item?id=9549245>

[ghaff]

Fairly price insensitive.

As I understood the exhibits in Greenwich, the Harrison clocks were largely eclipsed by cheaper versions by the time payment issues were resolved and they made it into widespread production.