> 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. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
