[time-nuts] Sidereal time

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Fri Jan 15 14:16:10 UTC 2010


This is all quite interesting.  6 years ago, for the MER rovers, I cobbled
together a scheme to drive off-the-shelf 24hr electric clocks off a 3325A to
run on Mars time (which is slightly slower than Earth time).  Same scheme
can be used for sidereal time, or to make an indicator that runs at varying
speeds (e.g. If you wanted to make a sophisticated tide clock or moon clock
or something).  A microprocessor which adds/drops pulses in the 32.768 kHz
reference input is probably the cleanest way.


On 1/15/10 1:27 AM, "Hal Murray" <hmurray at megapathdsl.net> wrote:

> 
> 
>> 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.
> 
> Sounds good to me, but since this is time-nuts, you need a GPIB connection to
> the synthesizer so you can tweak it to track the details from IERS.
> 
> It would be interesting to work out the details and see which is the
> most-significant digit that changes.  Would you need to tweak the synthesizer,
> or are the changes off the bottom?
> 
> 
> 
> Plan B:  Do it in software.
> 
> Consider a small CPU running from 10 MHz that can drive a display.  If it has
> a connection to the outside world, then you can tell it how many ticks per
> sidereal second and when to start using the new value.
> 
> Small LCDs are not expensive.  There are some designed to fit into a disk/CD
> slot on PCs.
> 
> 
> SparkFun has Arduinos for $30 and LCDs for $14 and up.  Some assembly
> required.
> 
> Or get their Serial Enabled LCD for $30 which includes a PIC16F88 and figure
> out how to reprogram it to keep time.
> 




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