[time-nuts] Setting clocks 100 years ago

[Jean-Louis Oneto]

Other Timeballs that I know are at USNO (Washington DC) and Real 
Observatorio de la Armada (ROA, San Fernando, Cadiz, Spain).
Regards,
Jean-Louis
----- Original Message ----- 
From: "Dave Brown" <tractorb at ihug.co.nz>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Friday, November 05, 2010 11:37 AM
Subject: Re: [time-nuts] Setting clocks 100 years ago


> Another existing sample of a time ball station close to home (for me) is 
> here in Lyttelton near Christchurch, NZ (quake city)
> http://www.teara.govt.nz/en/timekeeping/2/3
> It too suffered some building damage in the recent seismic event but will 
> no doubt be restored in due course.
>  Worth a look if you're ever out this way.
> DaveB, NZ
>
> ----- Original Message ----- 
> From: "Murray Greenman" <Murray.Greenman at rakon.com>
> To: <time-nuts at febo.com>
> Sent: Friday, November 05, 2010 12:30 PM
> Subject: [time-nuts] Setting clocks 100 years ago
>
>
>> Navigators used chronometers to determine their longitude. If they were
>> stopped in one place long enough, they could work out longitude by a
>> complicated process of star and lunar observations; however, when they
>> left an established port, they usually took with them a time standard
>> based on local measurements of the sun and the known location of the
>> port.
>>
>> These measurements used a device called a 'Transit', which was a simple
>> telescope mounted so that it pivoted in elevation, but was fixed N-S in
>> azimuth. Midday was marked by the time at which the sun transited the
>> telescope. It thus had higher resolution than a sundial. Getting N-S
>> axis correct involved determining by iteration and surveying the axis
>> that gave maximum elevation at time of transit.
>>
>> Once the transit was observed, a large ball on top of the building was
>> dropped, indicating midday, and in some locations a cannon was also
>> fired. Ships in port could observe the ball drop and hear the cannon. To
>> this day the ball drops at midday at Greenwich.
>>
>>
>> 73,
>> Murray ZL1BPU
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at 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 at febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.