Brooks Harris wrote:
On 2014-11-04 04:59 PM, Zefram wrote:
(Contrary to Brooks's earlier statement, the table does not
imply anything about pre-1972 UTC.)
I don't understand why you say that. Can you explain what you mean?
It seems to me the origins of both PTP and NTP are certainly
pre-1972 UTC.
Gerard Ashton ashto...@comcast.net wrote:
For example, the Standards of Fundamental Astronomy subroutine iauDat
provides the delta between TAI and UTC, and the source code comments say
UTC began at 1960 January 1.0 (JD 2436934.5) and it is improper to call
the function with an earlier date.
Michael Deckers via LEAPSECS leapsecs@leapsecond.com wrote:
| On 2014-11-04 19:45, Brooks Harris wrote on the history of UTC:
|
| For purposes of astronomy, and probably others, the rubber \
| band era may have
| relevance. To call it UTC seems a bit of a stretch to me, but there's no
|
On Wed 2014-11-05T11:11:38 +, Tony Finch hath writ:
Does anyone know where SOFA iauDat got its data for 1960 from? Because
that predates the USNO table.
I suspect they are the data from US NBS which Seidelmann included in
the Explanatory Supplement. The numbers from BIH Bulletin Horaire
On Wed 2014-11-05T11:11:38 +, Tony Finch hath writ:
Does anyone know where SOFA iauDat got its data for 1960 from? Because
that predates the USNO table.
By the way, which USNO table is that?
I'm wondering if it is actually a reprint of the BIH table.
--
Steve Allen
On Nov 4, 2014, at 2:52 PM, Michael Deckers via LEAPSECS
leapsecs@leapsecond.com wrote:
On 2014-11-04 12:34, Zefram wrote:
UT1 always ticks a second for that ERA increase, but Warner's point
is that the second of UT1 isn't an *SI* second.
It is not, and cannot be a SI second, except
On Nov 4, 2014, at 6:07 AM, Zefram zef...@fysh.org wrote:
Warner Losh wrote:
Users can only get UTC(foo) or a signal derived from UTC(foo) (e.g.,
traceable to NIST) and never UTC itself. Of course they can get to a
putative TAI(foo) trivially (I say putative, because as far as I know, no
Steve Allen s...@ucolick.org wrote:
By the way, which USNO table is that?
http://maia.usno.navy.mil/ser7/tai-utc.dat
Tony.
--
f.anthony.n.finch d...@dotat.at http://dotat.at/
Southwest Forties, Cromarty, Forth, Tyne, Dogger: Northerly 4 or 5, becoming
variable 3 or 4, then southerly 5 to 7
Warner Losh wrote:
The markers aren't the same.
I was referring to the PPS marks in a time signal, and because TAI and UTC
tick the same seconds the marks work equally well for both. Taking MSF
as a specific example, the onset of each per-second carrier-suppressed
interval (specifically, the
On Wed 2014-11-05T15:49:05 +, Tony Finch hath writ:
Steve Allen s...@ucolick.org wrote:
By the way, which USNO table is that?
http://maia.usno.navy.mil/ser7/tai-utc.dat
Yes, that is the table from the BIH, who were given responsibility
for the coordination as of the beginning of 1961.
On Wed, Nov 05, 2014 at 04:27:19PM +, Zefram wrote:
UTC is always
an integral number of seconds offset from TAI, and so by construction
UTC(NPL) is always an integral number of seconds offset from TAI(NPL).
I don't see how the first follows from the second here, particularly
if you
David Malone wrote:
if you transmit a second boundary at what you later identify to be
the wrong time, you can correct for that in your paper estimate of
TAI(X) so that it does may not align with UTC(X).
That's not what I mean by TAI(k). You're describing having two distinct
time scale
On 2014-11-04 22:26, Steve Allen wrote:
Guinot explained this using the term graduation second
in section 2.2 of 1995 Metrologia 31 431
http://iopscience.iop.org/0026-1394/31/6/002
He points out that the way the IAU has written the definitions of the
time scales uses a subtly ambiguous
On 2014-11-05 11:28, Steffen Nurpmeso wrote:
Oh, the German Physikalisch-Technische Bundesanstalt (PTB) also
has a general -- at least -- overview of the set of problems.
(English: [1] and all around that; oops, not everything is
translated, what a shame! I hope it's not due to lack of
On 2014-11-05 16:27, Zefram wrote:
... UTC is always
an integral number of seconds offset from TAI, and so by construction
UTC(NPL) is always an integral number of seconds offset from TAI(NPL).
Hence each of the marks also occurs at the
On Nov 5, 2014, at 10:54 AM, Zefram zef...@fysh.org wrote:
David Malone wrote:
if you transmit a second boundary at what you later identify to be
the wrong time, you can correct for that in your paper estimate of
TAI(X) so that it does may not align with UTC(X).
That's not what I mean by
On Nov 5, 2014, at 1:59 PM, Michael Deckers via LEAPSECS
leapsecs@leapsecond.com wrote:
On 2014-11-05 16:27, Zefram wrote:
... UTC is always
an integral number of seconds offset from TAI, and so by construction
UTC(NPL) is always an
On Wed 2014-11-05T14:50:06 -0700, Warner Losh hath writ:
On Nov 5, 2014, at 1:59 PM, Michael Deckers via LEAPSECS
leapsecs@leapsecond.com wrote:
The symbol TAI(k) is defined in
RECOMMENDATION ITU-R TF.536-2: Time-scale notations
of 2003 with the text:
At the time, I couldn't find
Despite what the recommendations might say, I think the TA(k) reported in the
Circular T are not efforts by lab K to realize TAI. They are probably
unsteered timescales generated by the labs for their internal use. The values
for USNO and NIST are extremely large, for example. That whole
In message 001601cff930$51f99010$f5ecb030$@comcast.net, Gerard Ashton write
s:
There was some discussion of transmitted vs. paper time scales.
This is another outdated notion.
Paper time-scales only exist because we couldn't do any better when
we had to wait for the astronomers to mail
Paper time-scales only exist because we couldn't do any better when
we had to wait for the astronomers to mail a letter to Paris with
their observations.
Today with realtime global clock comparisons available, both GPS
phase and point-to-point via sat/fiber, the only contribution in
the paper
if you are trying to measure UT1, it still takes time to correlate
the VLBI data and reduce it, and then send the results
to the right people, which doesn't happen without delay. (pardon
the pun). Synching up cesiums, hydrogen masers, and rubidium
fountains can happen much faster than it used
Despite what the recommendations might say, I think the TA(k) reported in the
Circular T are not efforts by lab K to realize TAI, since it is hard to imagine
how a lab could get a different offset attempting to realize TAI from
attempting to realize UTC. The values for USNO and NIST are
On Nov 5, 2014, at 4:43 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote:
For all practical purposes we could dismiss with paper clocks
and go real time, but I'm sure astronomers will tell us that
would do things to the cows milk or something...
All depends on your definition of “paper clock”
In message 545ac54a.10...@cox.net, Greg Hennessy writes:
I'd hate to get in Poul's slandering of astronomers, but if
you are trying to measure UT1, it still takes time to correlate
the VLBI data and reduce it, and then send the results
to the right people, which doesn't happen without
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