[time-nuts] Sidereal time

[J. Forster]

If you are going to do that computation, HP has a Digital Display (59304A)
for the GPIB in the very same family of instruments.

-John

==================

> Sidereal Time is another form of Earth Orientation angle based time
> where the orientation angle reference is the "fixed stars" instead of
> the mean sun.
>
> You need to take such effects as precession, nutation and polar motion
> into account.
> The rate isn't uniform with respect to atomic time.
>
> The (rate) ratio of UT1 to mean sidereal time is defined to be
> 0.997269566329084 − 5.8684×10−11T + 5.9×10−15T², where T is the
> number
> of Julian centuries of 36525 days each that have elapsed since JD
> 2451545.0 (J2000).
>
> If you are using UTC broadcasts to determine Sidereal time, you first
> need to correct UTC to obtain UT1 by applying the correction DUT1 ( UTC
> -UT1).
> DUT1 predictions etc are available from IERS.
>
> Bruce
>
> Neville Michie wrote:
>> It is an interesting question, we are so used to WWV and GPS with
>> regular time signals to synchronise clocks to mean solar time.
>> One method is to get a pocket calculator to identify a time in the
>> future when a siderial second nearly corresponds to a UTC second
>> and use the PPS pulse from GPS to jam a preset time into the Siderial
>> clock, (or start a halted clock with the correct time preset.
>> How long you have to wait for corresponding seconds depends on how
>> accurate you want it.
>> cheers, Neville Michie
>>
>>
>>
>> On 15/01/2010, at 2:25 PM, Bruce Griffiths wrote:
>>
>>> Brian Kirby wrote:
>>>> I would like to have an electronic clock to keep sidereal time. I am
>>>> planning on using a HP 59309A, which can except an external clock of
>>>> 1/5/10 Mhz.
>>>>
>>>> According to Wikipedia sidereal time is 23 hours 56 minutes and
>>>> 4.091 seconds - a total of 86,164.091 seconds
>>>>
>>>> So 86,400 seconds for a normal "atomic defined" day divided by
>>>> 86,164.091 = 1.002,737,903,89
>>>>
>>>> If I set the 59309A to 10 Mhz external clock and dial a synthesizer
>>>> up to 10.0273790, the unit should be able to keep sidereal time.
>>>>
>>>> Is my math and theory correct ?
>>>>
>>>> Brian - KD4FM
>>>>
>>> That just gives the rate.
>>> How are you going to set the actual Sidereal time to better than the
>>> 0.9s that can be deduced from UTC?
>>>
>>> Bruce
>>>
>>>
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