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.
