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Paul wrote:

"But now absolute measurements were possible, via an apparatus which drove an artificial star across the field of view and recorded the true crossing of the central wire vs. the observer's key tap. Thus each observer's work could be made free of his personal equation."

...and:

"Nevertheless, eye and ear is still the way we check a clock with a shortwave radio. When I find a time page on the Web dead accurate (or not) with respect to ticks from my radio, I wonder how much personal equation is present."

This reminds me of an app I have on my phone called "ClockSync". Its purpose is to synchronise one's phone clock with an NTP server. However, if the phone is not "rooted", the synchronization must be done manually. The app takes you to the phone's time setting screen and counts down the time until the next whole minute when the clock should be reset. It also plays a series of ticks for the last five seconds. Once you tap the "Done" button to reset the time on your device, you can see how close (in thousandths of a second) to the whole minute on the NTP server you got.

-Sean C.