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