[time-nuts] Sidereal time
Neville Michie
namichie at gmail.com
Fri Jan 15 04:04:06 UTC 2010
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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