[time-nuts] Sidereal time

J. Forster jfor at quik.com
Fri Jan 15 17:13:39 UTC 2010


Heresy:

Why do you really NEED super accurate siderial time? If you are using it
to point a telescope, you only need it accurate enough to get the guide
stars into the field. Remember, the atmosphere refracts kinda randomly.

-John

===============



> Hi
>
> Gee, there's an idea. Grab a TBolt and a simple micro. Hook them up to
> something like a Soekris and a big LED display. Network it up to get the
> latest offsets. Toss in a bit of wire and software and you get very high
> accuracy sidereal time.
>
> If NTP is "good enough" you could dispense with the TBolt and part of the
> wire. Tough to see the difference between NTP and GPS on a wall clock....
>
> Bob
>
> On Jan 15, 2010, at 4:27 AM, Hal Murray 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.
>>
>>
>> --
>> These are my opinions, not necessarily my employer's.  I hate spam.
>>
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>





More information about the time-nuts mailing list