[time-nuts] Clock Project Help

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Oct 29 20:42:26 UTC 2009


Hal Murray wrote:
>> I've been thinking of how to make a sidereal clock that's very
>> accurate. Things like time of coincidence between sidereal and UTC0 or
>> better UTC1 come  up. There are very few sources for UTC1.
>>     
>
> How far out do you want to go on the time-nut scale?
>
> A radio astronomy friend says they get UT1-UTC from USNO.  I haven't found 
> the page where it's published (yet), but I did find this one which has the 
> math for conversion to sidereal time:
>   http://aa.usno.navy.mil/faq/docs/GAST.php
> (Which brings up an interesting tangle, since the USNO gets some of their 
> data from VLBI.)
>
> The wiki page on DUT1 (UT1-UTC) (http://en.wikipedia.org/wiki/DUT1) says:
>   Forecast values of DUT1 are published by IERS Bulletin A.
>   Weekly updated values of DUT1 with 0.1 s precision are
>   broadcast by several time signal services, including WWVB.
>
> So if 0.1 second is good enough, listen to WWVB.  If you want better, try 
> this:
>   http://maia.usno.navy.mil/ser7/ser7.dat
> which starts:
>
>                                                                               
>
>       **********************************************************************  
>
>       *                                                                    *  
>
>       *                   I E R S   B U L L E T I N - A                    *  
>
>       *                                                                    *  
>
>       *           Rapid Service/Prediction of Earth Orientation            *  
>
>       **********************************************************************  
>
>       29 October 2009                                      Vol. XXII No. 043  
>
>
> It's got a table showing UT1-UTC for the next week to the microsecond (with 
> an error column of 5-7 microseconds).  It's changing at about 500 to 1000 
> microseconds per day so you might want to interpolate.
>
>
>
>   
see: http://www.iers.org/MainDisp.csl?pid=36-9
For longer term data.

Bruce




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