Hi Roger, Your analysis makes sense but I suspect that the explanation for the anomalies is the sundial was just badly designed. I don't think it's ancient; it looks to have been built within the last few decades.
It may have been modeled after a traditional monument but perhaps by someone not familiar with the functional requirements of a sundial. It wouldn't be the first example of bungled execution. Thanks for giving your attention to my question, John > On Apr 24, 2016, at 4:42 PM, Roger Bailey <[email protected]> wrote: > > Hello John, > > Yes, this is a puzzle. The sun on the solstice, 21 June, is at its lowest > altitude in the southern hemisphere. The noon altitude would be 47°. The sun > would rise and set on that day farthest to the north. This is an appropriate > new years day in the southern hemisphere to celebrate the return of the sun > as our new year in the north starting at the winter solstice. None of these > 21 June observations seem to relate to the "sundial". > > However other seasonal markers would be obvious with this sundial. One is the > winter solstice 21 Dec. On that date at the Tropic of Capricorn the sun at > noon would be directly above this sundial, casting no visible shadow. This > would explain the vertical orientation of the gnomon as the shadow could be > seen getting shorter as noon approaches and longer in the afternoon. > > The sloping east west gnomon could be used to note an approximate midway > point between the equinox and the solstice. When does the sun line up due > east and west at an altitude of 23.5°? The equation for the prime vertical, > the east west meridian, Sin Alt = Sin Dec / Sin Lat. This resolves to Sin Dec > = Sin23.5 x sin 23.5 and gives the declination as -9.15°. The east west sun > along the line of the sloping gnomon occurs around 17 Oct and 25 Feb. Perhaps > these were significant dates for the ancient culture in the area. > Pre-Christian cultures in Europe had such mid-season markers, Samhain 1 Nov > and Imbolc 2 Feb. were a couple of the names. A residual in Christian > cultures is Michaelmas and Candlemas > > The gnomon could also indicate the equinoxes as the sun rises due east and > sets due west in line with the gnomon. For early cultures marking the > calendar with seasonal markers was much more important than measuring the > time of day. > > Regards, > Roger Bailey > > > From: John Goodman <mailto:[email protected]> > Sent: Sunday, April 24, 2016 8:31 AM > To: Sundial List <mailto:[email protected]> > Subject: Tropic of Capricorn sundial > > I was recently in northern Argentina at the Tropic of Capricorn. I saw a > structure there that has been described as a sundial but I have trouble > understanding how it could work. I'm attaching a small photo of the gnomon, > which is angled at roughly 23.5 degrees. So far so good. > > What confuses me is that the gnomon is aligned along the east/west axis, > which you can see by the Google Maps satellite view shown for the coordinates > 23°26'52.1"S 65°21'06.0"W > > I've also read this description of the marker, automatically transited from > Spanish: > >> Generally, this place is chosen so that the natives of here come and >> celebrate the Inti Raymi, thanking the Sun on June 21, as the Incas used to >> do many years ago. They await the arrival of the Sun which for them is a new >> year. > > Would an east/west orientation be appropriate for a monument marking the June > solstice south of the equator? > > Thanks for your help deciphering the design, > John > > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > <>No virus found in this message. > Checked by AVG - www.avg.com <http://www.avg.com/> > Version: 2016.0.7539 / Virus Database: 4556/12091 - Release Date: 04/24/16
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