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 <[email protected] 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 <[email protected]> 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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