[time-nuts] Sidereal seconds

Neville Michie namichie at gmail.com
Fri Mar 2 11:43:17 UTC 2012


The theodolite is not a problem, I use a distant street lamp (4Km  
away) as a referred object (RO) to set azimuth,
and with the usual levelling it takes moments to set the co-ordinates  
of a chosen star.
The RO is observed by one of several methods to get a good azimuth.  
It is chosen to be visible by day or night.
Then I listen to the clock ticks and watch the star cross the  
graticule. The star co-ordinates are from an ephemeris.
You can repeat with the same star or others at later times.
I have not looked at the sidereal time on Lady Heather yet, I was  
unaware of it.

cheers, Neville Michie

On 02/03/2012, at 10:14 PM, mike cook wrote:

> Le 02/03/2012 05:13, Neville Michie a écrit :
>>
>> A possible solution is to take mean time (from a TBolt 10MHz) and  
>> divide it by 9,972,695.7 to give a PPS(sid) signal that can run a  
>> digital clock dial and give one second(sid) ticks to phase the  
>> pendulum. It may be simpler to divide by 9,972,696 to stay with  
>> integer division and have an error in the order of a second per  
>> annum. (which we have from leap seconds anyway).
>> TVB made some picDIV chips with a synch pin that do a similar  
>> task, but have I got the number correct?
>   number looks ok , at least according to the usual sources.
>> and are there other nuts that would like to add a sidereal clock  
>> to their clock vaults to make it worth while to make such a chip?
> Yup, I guess that would be a useful extension to the code.  You  
> would just need to change the delays to fit a 2493174 instruction  
> count for a 10MHz input.
>> If I set up the sidereal clock then I can use my theodolite to  
>> check time against the stars.
> More of a challenge I think. Harrison is reported to have used  
> occultation by buildings from a known observation point. It would  
> be probably be easier than keeping a theodolite precisely  
> orientated over long periods of time.
>> cheers,
>> Neville Michie
>> Sydney
>> Australia
>>
>> _______________________________________________
>> 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.




More information about the time-nuts mailing list