[time-nuts] Sidereal time

[Brooke Clarke]

Hi Brian:

Why?  Do you just want to see the sidereal time on a display or do you 
need a digital output?
The Spark Fun "serial enabled" displays use what's called a "back pack" 
that has the PIC 16F88 uC and it's used to do serial data to LCD 
parallel data can control lines.  I've made some clocks using that chip.
http://www.prc68.com/I/PIC16F88.shtml
http://www.prc68.com/I/PRC68COM.shtml#07092006

A friend is setting up an observatory where the pointing accuracy of the 
telescope mount is specified as " 7 arcseconds or less peak-to-peak 
periodic error before correction". Much better after correction.  That 
implies he needs to know what time it is within tens of milliseconds.
http://www.prc68.com/I/StellarTime.shtml#StrMov
We looked into different ways to get the time into his computer to that 
accuracy and NTP looks like it will fill the bill, so a GPS receiver may 
not be required.

Have Fun,

Brooke Clarke
http://www.PRC68.com


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
>
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