[time-nuts] Measuring sidereal/solar time?

Ilia Platone info at iliaplatone.com
Fri Dec 30 05:59:49 EST 2016

Another solution from ground can be radio observation using a precise 
interferometer: radio wavelengths are transparent to the earth 
atmosphere and there are various references like sun during day, and (if 
antennas are sensible) bright pulsars and other radio sources during night.

Best Regards,


On 12/30/16 10:42, Attila Kinali wrote:
> On Fri, 30 Dec 2016 10:59:03 +0200
> Anders Wallin <anders.e.e.wallin at gmail.com> wrote:
>> out of curiosity, are there any amateur/semi-pro experiments that can
>> measure the length of the solar or sidereal day to sub-millisecond
>> resolution?
>> To reproduce data like this:
>> https://upload.wikimedia.org/wikipedia/commons/5/5b/Deviation_of_day_length_from_SI_day.svg
>> Something in the sky that goes "ping" every day - detected with a pointing
>> accuracy of < 1ms/24h or <0.01 arc-seconds (!?). Or perhaps two
>> satellite-dishes pointed at the sun and noise-correlation/interferometry??
> I don't know of any such experiment already performed, but I am not up
> to date on what's going on in the hobby astronomy community.
> I am not sure whether sub-milisecond resolution is feasible, but
> I think the "easiest" method would be to do a "modern" version of
> an meridian telescope:
> Using a camera fix mounted (ie not moving and if possible vibration isolated)
> on a pedestal pointed at the sky, approximately looking south. A simple
> webcam would be probably enough for first experiments, as long as you get
> a good picture of the stars. A good compact camera which allows to use
> a remote shutter with a proper lens and exposure control should be better.
> Probably the best resource here are the people/websites that deal with
> book scanning, as they tend to automate the whole picture taking process.
> Using magic lantern (http://magiclantern.fm) with Canon cameras might
> give additional features needed for the task.
> >From the pictures taken, calculate the positions of the stars (by fitting
> circles onto the bright pixels) and figure out which star is which (using
> astronomical list of stars). For this step there is a plethora of open source
> astronomical software available, but I don't know how well they fit the task
> of figuring out what the position of the stars relative to the camera reference
> frame. After that, it's just some simple math of calculating the difference
> between the position of the stars and where you would have expecteded them
> at the time when the picture has been taken.
> Some usefull software projects are:
> http://astro.corlan.net/gcx/
> http://www.clearskyinstitute.com/xephem/
> http://starlink.eao.hawaii.edu/starlink
> http://astro.corlan.net/avsomat/index.html
> http://rhodesmill.org/pyephem/
> 			Attila Kinali

Ilia Platone
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Cattolica (RN), Italy
Cell +39 349 1075999

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