[time-nuts] Sidereal time

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Jan 15 09:35:16 UTC 2010


Really?? you'd better tell USNO, NRAO etc.

Bruce

mike cook wrote:
> No such thing as a siderial second.
>
> Le 15/01/2010 05:04, Neville Michie a écrit :
>>
>> 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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>
>
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