[time-nuts] Result of Earth Quake speeds up earth?

[jimlux]

On 3/15/11 11:08 PM, Bruce Griffiths wrote:
> jimlux wrote:
>> On 3/15/11 9:36 PM, Hal Murray wrote:
>>>
>>>>> If I were doing this in my backyard on a budget I'd mount a small
>>>>> telescope nearly straight up so that a bright star would pass through
>>>>> the field on several nights. I'd measure the light of the star
>>>>> through a slit and time the peak of the light each night. I bet I
>>>>> could get to about a microsecond. I'm wondering what professionals
>>>>> are doing in this field.
>>>
>>>> I have references for VLBI, if you want. You probably cannot do optical
>>>> accurately enough because of "seeing" effects, at least.
>>>
>>> What sort of accuracy can I get with:
>>> 1) small/medium telescope in suburban back yard
>>> 2) small/medium telescope out in the sticks
>>> 3) big telescope in a good location
>>>
>>
>> It's sort of time nutty...
>>
>> Couldn't you rig up a MLBI (medium, not very) setup between you and
>> someone else in your area..
>>
>> Could one detect pulses (or a signal) from some quasar (or "infinite
>> distance" stellar source) with a reasonable small antenna.
> Optical methods typically achieve positioning accuracies of around 10
> milliarcsec or so.
> Radio methods are about 100x more accurate or around 100 micro arc sec.
>
> To achieve the latter synchronisation between antennae has to be better
> than around 5us.
> However to get fringes from the spectral region around the waterhole
> then relative synchronisation between receivers of a few tens of picosec
> is required.




>
> Achieving such synchronisation even for an MLBI system would be
> something of a challenge without hydrogen masers or equivalent
> performance clocks at each antenna.
>
> With care integration times of around half an hour or so are possible
> using a hydrogen maser at one antenna and an SRS FS725 rubidium standard
> another antenna.
>> __
>
> Using common view GPS carrier phase observables may be an option as long
> as the MLBI system isnt too large.
>


Or, you can send a signal between the two stations by an RF link.  If I 
recall correctly, you'd need to compensate for propagation variations, 
but, a two way scheme might work for that.  I think I have a paper 
somewhere that talks about how they did that for VLA.