Hi If you go by Wikipedia, 10 ms per day was considered pretty good in 1909. Shortt clocks came along in 1929 and are mentioned as 1 second per year. I suspect the 2 ms / day and 1 sec per year numbers are both referring to a Shortt.
Simple answer is that all of this came along after you had electronics to compare stuff with. Calibration times were in months. Deviations between clocks in an ensemble were used to estimate shorter time periods. I don't find it to unbelievable that you could time an astronomical event to ~ 0.1 seconds or better without anything very fancy being involved. If you wanted to automate it, light sensors date back into the 1850's. Either way you could get data in less than a year that would confirm / deny your accuracy. Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed Sent: Thursday, January 27, 2011 4:13 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Clock Calibration Boy I sure don't know but. I could make some assumptions especially if it were 100 years ago. I might guess its either a sun or star track and the fact that exactly 24 hours later it crossed. Granted the clock could be adjusted so that its tick would exactly cross. Most likely a light/candle and a small mirror on the pendulum.... This would not account for any of the effects we consider today. Just my crazy useless way of thinking. Regards Paul On Thu, Jan 27, 2011 at 3:55 PM, Perry Sandeen <sandee...@yahoo.com> wrote: > List, > > I was reading some of the history of mechanical clocks and was astonished > to see that one guaranteed its accuracy to 2 milliseconds per day! (And it > was) Now this same clock when tested with modern equipment tested to be > accurate to 200 micro-seconds per day. Astonishing! > > This got to wondering how the heck they were able to calibrate a clock to > milliseconds per day back then? > > And as extension to that question, how do they prove the accuracy of F1 or > other similar time standards? > > Regards, > > Perrier > > > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.