[time-nuts] Sidereal time

Jim King jim at jimking.net
Fri Jan 15 20:20:30 UTC 2010


I'm not sure your friend needs the time at all.  Telescope tracking 
mounts have a periodic error due to non-perfect mechanical parts.  The 
usual way to remove this error is to "train" the mount by manually 
guiding it through one or more periods, or - probably more common these 
days - use an optical autoguider.

Jim

On 1:59 PM, Brooke Clarke wrote:
> 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





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