[time-nuts] Calculating sidereal time

[Brooke Clarke]

Hi Didier:

I'm still very much interested.  The main reason is the GPS satellites come close to following the same ground track.
So I'd expect the elevation and azimuth to a given SVN to be the same on a 12 sidereal hour basis.

-- 
Have Fun,

Brooke Clarke
https://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.

-------- Original Message --------
> Actually not a specific requirement. I made (and am in the process of
> making a new batch of) an assembled kit which is used to monitor the data
> stream from a Trimble Thunderbolt GPSDO and display time and vital
> information on a small LCD display.
>
> A long time ago, Brooke Clarke, on this list asked if I could make it
> display sidereal time. I had no idea what it was so I researched it and
> found out I needed to be able to process double precision calculations,
> which the original 8 bit microcontroller was totally incapable of.
>
> So I set this aside but I recently came across an inexpensive ARM chip and
> decided to make a new version of my monitor with it. The toolchain is
> excellent and supports double precision so I decided to fullfil Brooke's
> request, who by now has probably lost interest in it but for the fun of it
> and to learn something.
>
> So while I understand sidereal time is used by astronomers, I am not one so
> I have no personal practical use for it, which has the advantage of setting
> the bar pretty low to decide when I am done :) That said, I am open to
> suggestions to actually make it more useful if possible.
>
> It is so easy to load an app in your phone if you actually need sidereal
> time that I do not believe my kit will be used for that purpose but it was
> an interesting exercise for me and I am glad it is working.
>
> I learned quite a bit and discovered, through your postings and the
> associated links how complex that subject actually is.
>
> I love this list.
>
> Didier KO4BB
>
>
> On Sat, Jan 19, 2019, 8:01 PM Steve Allen <sla at ucolick.org wrote:
>
>> On Sat 2019-01-19T12:15:28-0800 Steve Allen hath writ:
>>> The most expedient place to find them are roughly pages B7 to B12 in a
>>> current Astronomical Almanac.  See for example
>>>
>> https://babel.hathitrust.org/cgi/pt?id=uc1.31822038913307;view=1up;seq=116
>>
>> Emphasizing one point, it has always been important to use expressions
>> for GMST and such things which are designed for use in the same
>> reference frame as the star catalog.  Current star catalogs do not use
>> an equinox as any kind of reference point, therefore any expression
>> for GMST does not simply correspond to the longitude-like coordinate
>> of a current star catalog.  GMST now coresponds to a new fictitious
>> point in the sky which is defined with much more complexity than in
>> the old days.
>>
>> What exactly is the intended use case for this project?
>>
>> --
>> Steve Allen                    <sla at ucolick.org>              WGS-84 (GPS)
>> UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat
>> +36.99855
>> 1156 High Street               Voice: +1 831 459 3046         Lng
>> -122.06015
>> Santa Cruz, CA 95064           https://www.ucolick.org/~sla/  Hgt +250 m
>>
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