[time-nuts] Setting clocks 100 years ago

[Bob Camp]

Hi

Consider that the Harrison Chronometer had accuracy specs of < 2 minutes
over a months long voyage. His later marine clocks got to seconds / month
levels. Stationary clocks of the same era were doing sub-second/month type
accuracies in a "good" environment. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bill Hawkins
Sent: Friday, November 05, 2010 11:00 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Setting clocks 100 years ago

I remember the ball dropping at Greenwich at noon GMT, but that's
because it was summer, and 1 PM BST. Makes you wonder how they
interpolated the hour after the noon transit. Chronometers must
have been pretty good by then, or there would have been no
point to generating a time signal.

The US Navy dropped the ball at noon when it dropped a ball.

See http://wwp.greenwichmeantime.com/info/timeball.htm

People who didn't have a ball and mast used a "noon gun." These
were also used inland. I remember seeing (on TV) one of them
with an arrangement that use magnified light from the sun to
light the fuse on the cannon.

If you Google "noon gun" you will be flooded with information
about the cannon on Signal Hill in Cape Town, SA. Use the advanced
search to reject "Cape Town" and many other locations will appear.

Bill Hawkins


-----Original Message-----
From: Rob Kimberley
Sent: Friday, November 05, 2010 3:31 AM

I thought the ball dropped at noon. Perhaps you were there in the summer,
and they had advanced 1 hour for summertime (daylight savings).

Rob K


Bob Marinelli wrote:

> Hi Murray,
>
> Actually, the ball at Greenwich drops at 1:00 pm every day.  For 
> everyone who can get to London, the observatory is well worth at least 
> a half day visit, they have several working Harrison clocks and yes 
> you can set your wristwatch at 1:00 when the ball drops :) there is 
> also a wonderful transit.
>
> Cheers,
>
> Bob
>
> On Nov 4, 2010, at 4:30 PM, Murray Greenman wrote:
> >
> > 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
> >


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