[dghlsakjg]

It depends on the maker, not all quartz watches are equal. However, quartz is typically very stable as an oscillator over the conditions that humans can survive in. That’s why we use it in watches after all.

That said, I have used a quartz watch (mid level Citizen) for actual celestial navigation at sea. It is, for all intents and purposes always going to be more accurate than mechanical (mine typically is good for ~1 second per month, and always in the same direction) Certified mechanical watches typically vary more than that in a day, I believe the standard is 2 seconds per day. I don’t know what a proper marine chronometer is certified to, but it is worth pointing out that a marine chronometer is typically not exposed to the conditions you describe at sea. The official ships chronometer is always kept down below, protected in what is effectively a gimballed humidor. For the purposes of navigational measurements, you use your wrist watch at the time of sighting on deck and add or subtract the difference between your watch and the chronometer. To add on to all that, if a ship is rolling and pitching like you describe your chances of an accurate sight are very low. Even in perfect conditions, it is hard to call the exact moment of alignment to within a second.

If I placed my quartz watch in the box with the official chronometer, I am perfectly willing to argue that if there is a discrepancy in the times shown, the quartz watch should be trusted.

[defrost]

> To add on to all that, if a ship is rolling and pitching like you describe your chances of an accurate sight are very low

You as a human wouldn't shoot a line in those conditions, no.

The point is that mechanical clock mechanisms endure those conditions .. the rise and fall of tempreture, the rise and fall of air pressure, the shock of acceleration (even when sharply reduced by a gimbal mount).

The error bar over months at sea is the tension betwen the drift effect of all those conditions and normalising complications - gimbal mounts, the use of bimetallic strips to counter tempreture change expansions, etc.

In dead calm conditions a mechanical clock at sea carries the accumulated drift baggage of past storms and heatwaves.

Circling back to quartz oscillators, my question above goes to prompting others to ask themselves if an electronic oscillator regulated by a quartz crystal shows any performance differences over a year when harsh real world physical usage conditions are compared to ideal controlled test conditions.

Does temperature affect the oscillator, does humidty, air pressure, accumulated shock forces, etc.

Addendum:

   I cant imagine why an instrument that is ~40x less precise would offer more precise timekeeping

~ @dghlsakjg

  I'm having some difficulty understanding how [..] will have less of an effect on a fragile mechanical system than a tuned electronic one.

~ @TheOtherHobbes

I've reread both my comments above and I'm having some difficulty seeing they can be read to take away a claim that a mechanical marine clock is more accurate than a quartz timekeeping mechanism. Both comments address accuracy in harsh variable conditions versus stable STP lab conditions.

See also: Precision vs. Accuracy - https://manoa.hawaii.edu/exploringourfluidearth/physical/wor...

[dghlsakjg]

To answer your question directly.

A mechanical timepiece that calls itself a marine chronometer has to be accurate to +-0.5 seconds per day.

The most accurate quartz wristwatch is certified accurate to +-5 seconds per year.

My experience, in the exact harsh real world conditions that you are talking about, is that is a realistic expectation for quartz watch to accomplish. I cant imagine why an instrument that is ~40x less precise would offer more precise timekeeping