Kevin, I am excited about your article "Basic Astronomy for the Gnomonist." It will take some time to digest, but it seems to have a very nice graphic analysis for the many formulas and solar positioning we deal with. I appreciate you making this reference available.
I think what you call a Hectoromos dial is what I have heard described as a Singleton dial. Here is a link to a similar (vertical) dial at the University of Vermont. Fred Sawyer wrote about the Hectoromos dial in an early NASS compendium. I think Plato might have had something to do with it. -Bill On Sun, Feb 23, 2014 at 2:32 PM, Kevin Karney <[email protected]> wrote: > Dear Friends > > I have spend many happy hours during this wet, wet winter investigating > and learning how to calculate all the solar parameters that a > gnomonist might possibly need - Equation of Time, Declination, RA, > Altitude, Azimuth, Time of Sunset/Rise, etc, etc. > > I have been surprised to find that - with traditional calculation methods > and an absolute minimum of astronomical information - it is possible to > calculate everything from first principles to a surprising degree of > accuracy. > > Other than location and local time, only six pieces of astronomical > information are required - obliquity, eccentricity, Sun's GHA at 1/1/2000, > longitude of perihelion, a single precessional constant and the length of > the tropical year. Accuracies for the EOT are +/- 2 seconds of time For > altitudes/azimuths, less than 1 minute of arc - much better than needed by > most gnomonic problems. > > If any of you are interested in such calculations, I have loaded a > document with all the astronomical theory and background plus the code onto > my website > *www.precisedirections.co.uk/sundials > <http://www.precisedirections.co.uk/sundials>* > The code is written in Python, a language available on every type of > computer, which is very easily understood, quite easily learnt and very > easily translated into any other coding language you might like. > > If you own an iPad or iPhone, and are prepared to buy a cheap little app > called Pythonista, the code will extract locational & time information from > your phone - so you do not even have to input this to get your calculations > done > > You might also like to see a graphic of a civil mean time horizontal dial, > which *I think* is called a hectomoros dial, that is destined for my > garden. This is also on the website. > > Enjoy > Kevin > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > >
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