...and it seems to me that the South-Solstice of 2017 occurred on December 21.686, where the time of day is expressed as a fraction of a day, appended to the date.
Michael Ossipoff 41 F On Fri, Oct 4, 2019 at 7:15 PM Michael Ossipoff <[email protected]> wrote: > Autumn doesn't begin at the autumnal equinox. The terrestrial seasons and > the astronomical-quarters are entirely different things. The > astronomical-quarters begin at the equinoxes and solstices. The terrestrial > seasons are terrestrial, though of course they're caused by, and lag > behind, the Solar-declination. The lag-time is different at different > locations, and perceptions about winter, spring, summer and autumn are > subjective, and differ geographically because of differing time-lag and > naturally-later arrival of perceived spring or summer in colder places, etc. > > No one believes that winter north of the equator really doesn't begin > until December 21st. > > The Sun is the physical origin of the Earth and its life, and the source > of the energy for life on Earth, and the cause of the seasons, but the > seasons don't begin on the astronomical-quarters. > > Michael Ossipoff > 41 F (South-Solstice WeekDate Calendar) > > ...Friday of the 41st week of the calendar-year that began on the Monday > that started closest to the South-Solstice (Winter-Solstice north of the > equator). > > ...or closest to the *approximated* South-Solstice based on the > assumption that a South-Solstice occurs exactly every 365.2425 days, > starting from the actual South-Solstice of 2017. > > The 365.2425 is from a determination that I once made of the average > length of the South-Solstice tropical-year, from 2000 to 2050. The fact > that 365.2425 is also the length of the Gregorian mean-year is coincidental. > > > > > On Fri, Oct 4, 2019 at 8:59 AM Frank King <[email protected]> wrote: > >> Dear Hervé, >> >> Congratulations on your comments on my >> puzzle about the September Equinox last >> month... >> >> > It seems that the answer to your question >> > can be found in the attached picture >> > inclosed in a recent information letter >> > issued by the French IMCCE institute >> > specialised in celestial mechanics and >> > ephemerides calculations >> >> This gives us three times of interest on >> 23 September 2009: >> >> 07:49:51.80 Right Ascension = 12h >> >> 07:50:11.81 Solar Longitude = 180 >> >> 07:50:15.58 Solar Declination = 0 >> >> Call this the FRENCH solution. >> >> If you have an Android cell 'phone you >> can look at Sol et Umbra which gives >> these times on 23 September 2009: >> >> 07:49:49.40 Solar Declination = 0 >> >> 07:50:09.25 Solar Longitude = 180 >> >> 07:50:32.50 Right Ascension = 12h >> >> Note that the events occur in reverse >> order! Call this the ITALIAN solution. >> >> Now use the JPL Horizons program: >> >> https://ssd.jpl.nasa.gov/horizons.cgi >> >> I don't have a proper computer at the >> moment but here are three values I found >> (using my 'phone) for the single time: >> >> 23 September 2019 07:50:12.00 >> >> Solar Declination = 00:06:13.3 >> >> Solar Longitude = 180.0019964 >> >> Right Ascension = 11:59:01.94 >> >> The declination has not yet dropped to >> zero. >> >> The longitude has gone past 180. >> >> The Right Ascension has not yet >> reached 12h. >> >> Call this the U.S. solution. >> >> Moral: never believe a single source >> of information :-) >> >> If you think you can see the pattern, >> try using the Horizons program to >> investigate the March Equinox in >> 1718. Using the Gregorian Calendar, >> we find: >> >> The Right Ascension went to zero >> late on 16 March (just before >> midnight). >> >> The declination went through zero >> about the same time on 16 March. >> >> The solar longitude reached zero >> on 21 March. FIVE DAYS LATER!!! >> >> So you see: there is still a little >> bit more of my puzzle to unravel!! >> >> Very best wishes >> Frank >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >>
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