The most accurate wristwatch ever?

[Otis]

Came across this little bit of info earlier this week, thought I'd share it.
Once again, it shows just how well-made some of the brands that are considered 'low-end' are.

The Citizen Citizen Crystron Mega or 'Mega Quartz'. c.1975!



Considered by many as the most accurate wristwatch. Whilst most quartz watches were within 15seconds per month, the citizen mega quartz/Citizen Crystron Mega was accurate to 3 seconds per year. Per year, people!
A bit of info on it's 'thermocompensated' quartz movement:
Stability in a quartz watch's rate, comes down to the cycles/beats of its resonator, the quartz crystal. Apparently, the crystal actually moves, many many thousand times per second. The fact that they have such a high oscillation rate negate traditional factors that effect a rate, ie: arm movement, watch position, gravity and so on. However, one small drawback appears to be that it is affected slightly by temperate, which has been the greatest cause of rate difference in quartz watches.

One way of reducing error rate is to keep the crystal at a constant temperature, as is done with some laboratory instruments by keeping them in an oven of sorts. Now, carring an oven is not only uncomfortable, but also impractical. But, it seems that just wearing your watch on your wrist has a similar effect! The temperature of your body varies less than ambient temperatures, therefore your watch is always next to a (relatively) constant temperature. Also, those clever buggers who make the crystals have used their physical properties to best advantage: at a particular temperature point, the various idiosyncrasies within the crystals start to cancel eachother out. This point sits around 28 degrees celsius, or 'wrist temperature'.
HOWEVER.... if the temp varies greatly, the rate is affected. This is where 'thermocompensation' kicks in:

Among many methods used, the Citizen in question had a very, very high frequency crystal (4MHz). I don't really get it, but I'll try and simplify it...
They also have a different crystal orientation, and the relationship between these enables a broader range of temperature over which the rate is constant.
There are a few different methods, one of which the Oysterquartz utilised, but I really cant explain them clearly....so, check out this link, a damn good read. It talks about the OQ as well:

http://forums.watchuseek.com/showthread.php?t=2087

Back to the citizen.... IMO it's a ugly looking, watch, it was made with case and band in one piece, 18K gold, the battery lasted 1 year, only 3000 were made and it cost more than $15,000. But, what a hell of a piece of engineering. Reading about all of this really was interesting, and gave me a lot of respect for the quartz phenomenon!


(Apologies to all if I screwed up in trying to explain it, i'm no scientist and it bloody confusing at times!)