[time-nuts] Clock Calibration

Alan Melia alan.melia at btinternet.com
Thu Jan 27 23:36:25 UTC 2011


Hi This is an interesting concept of measuring or comparing without
electronics. Dont forget the scientists of former eras has some quite
inovative bits of kit..... the CRT dated from the 1920 but Victorians used a
sooted glass slide carried on a small trolley that was moved by a falling
weight.....a storage 'scope forsooth :-)) I believe you will find Bell used
a similar item in his speech investigations. Also, yes time was cheaper then
so a test period of days would be acceptable......it only very recenly we
have become so impatient :-))
It would probably be relatively easy to divide the swing of a long pendulum
up in to 10ths or even 20th of a second ....and your reference would be a
transit telescope, or, I believe, the Moon and a church steeple ?? was that
Harrisons early work with the all wooden  mechanisms?

Alan G3NYK

----- Original Message ----- 
From: "Bob Camp" <lists at rtty.us>
To: "'Discussion of precise time and frequency measurement'"
<time-nuts at febo.com>
Sent: Thursday, January 27, 2011 9:56 PM
Subject: Re: [time-nuts] Clock Calibration


> 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-bounces at febo.com [mailto:time-nuts-bounces at 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 <sandeenpa at 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
> >
> >
> >
> >
> >
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