[time-nuts] Clock Project Help

Hal Murray hmurray at megapathdsl.net
Thu Oct 29 19:03:44 UTC 2009

> 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:
(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 
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.

These are my opinions, not necessarily my employer's.  I hate spam.

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