Hi Brooke, SV position in circular orbit repeats at 12h sidereal, but ground relative az/el repeats at 24h sidereal. This is because of the earth 24h rotation rate. After 12h your earth position will be 180deg away from (inertil) start position.
— Björn Sent from my iPhone > On 21 Jan 2019, at 03:35, Brooke Clarke <[email protected]> wrote: > > 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 >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >>> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
