Re: R: Re: A very interesting dial
Dear Frank, Gianni, Robert, Bill and all, It seems that there is much interest in directly solving the multibody Kepler's law for at least those objects in our solar system. This is working from near basic principles rather than developing perturbations to curve fitting polynomial circular functions. The method allows for extremely good extrapolation rather than just the extremely good interpolation of of the trigonometric series approach. Trigonometric series may be the most efficient approximation methods, but cover only a very restricted range of the variables outside of which they fall apart rapidly. The method may seem, and in fact may be overkill, for the data extraction required to design and build a sundial but, a sundial is a fitting monument to the achievement of the method! Edley. --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: R: Re: A very interesting dial
Dear Gianni, Mea culpa! You are of course right. The summer solstice arc indeed curves upwards on a cylindrical surface. I was assuming that the surface was made of flat segments (as in the external photograph) but this is not so. > - The higher line (at ¾ of the height of the > doors) (aluminium) is the 70° almucantarat > (constant-altitude curve) I hadn't noticed this but, again, you are right. Yes, I agree with that. > - The compass rose is of 24 points because from > each of them comes out one of the vertical azimuth > lines True, but azimuth lines are usually separated by 22.5 degrees or 11.25 degrees. > I don't understand why the planners have used a > program that solves Kepler's Laws... I agree. Kepler's laws are fine for an ideal case but the Earth's orbit is much more complicated than pure Kepler. A good exercise is to implement the Meeus algorithms. This takes a long time but when you have finished you understand how messy the Earth's orbit really is! Best wishes Frank --- https://lists.uni-koeln.de/mailman/listinfo/sundial
R: Re: A very interesting dial
Molto bella ! Very Fine ! From Google Earth we have Lat.=39d 38’ Long. =104° 56’ 25” E - the place is almost exactly on the 105d meridian with TZ=7h East (englewood, colorado,4000 quincy ave.) In my opinion : - the arc that touches the bottom of the noon analemma is certainly a part of the solstice line (brass) - The higher line ( at ¾ of the height of the doors) (aluminium) is the 70° almucantarat (constant-altitude curve) - The inside is a cylindrical surface with a radius of about 200 cm (80”) and with a conical roof with a slope of 26.9 d (=90-Lat-23.45) - The higher altitude curve ( third photo) is the 30d almucantarat - The compass rose is of 24 points because from each of them comes out one of the vertical azimuth lines I don't understand why the planners have used a program that Because of the fact that the year doesn't have an integer number of days it is necessary, in the calculation of sundials, to take into consideration not the exact values of the declination and of the TEq , but their mean values calculated in a period of at least 4 years (without considering the 29 February :-) ) Also a digital clock < to check the solar clock's accuracy> seems to me a little excessive. Gianni Ferrari P.S. One of my old programs calculates and draws these kind of sundials >Messaggio originale >Da: Frank. [EMAIL PROTECTED] >Data: 20-mag-2007 22.01 >A: "Robert Terwilliger" <[EMAIL PROTECTED]> >Cc: "Sundial Mailing List" >Ogg: Re: A very interesting dial > >Dear Robert, > >Indeed that is a very interesting dial. > >Do you have any idea what the arc is that touches >the bottom of the noon analemma? It can't be a >short length of constant-declination curve because >it is the wrong way up and it can't be a short >length of constant-altitude curve either (that >would be level on a true cylinder). > >The outside of the building suggests that the >cylinder is made up of flat faces. It is less >clear that the inside is also flat faces. > >Other random thoughts: > > 1. A problem with domed nickel nail heads is >that you get dazzling reflections at the >critical moments. > > 2. The compass rose is of 24 points. I am more >used to 8, 16 or 32 points. How common > are 24-point compass roses? They are >suggestive of hours of course but only >very loosely. > > 3. Any chance that 29 February features? :-) > >Frank King >Cambridge, U.K. > >--- >https://lists.uni- koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
