Hello all To my surprise this time I heard more from the silence of others than from the advices.
Chris Lusby gave me a very good and practical example on how to see what happens when I build a certain dial with a 20km-long gnomon. Nevertheless, I've had a small engineering problem in building it. Something easy to overcome, like several truckloads of dollars and a few years of hard work. Of course, these difficulties will not prevent me from builing it! No, mot me! ;-) Back to seriousness. I now think my mistake was quite simple (as it was to be expected). Basically it was a matter of how to measure and express the declination of a wall. I had understood -- I mean, misunderstood -- that a declination was to be measured for each wall against its meridian if facing North or South; or against its East-West line, if facing East or West. In summary, I was calculating a sundial for a declination of, say, 20 when it was in fact 70 or 110. Once I fixed that and measured the angles of declination against the meridian for every face things started making sense and I got three more handsomely consistent dials. At least on the paper (since I am travelling I have not had the opportunity to check them with a working model). And I even know where my misunderstanding came from. Albert Waugh's notation for a declining sundial is "we would say this wall declines S 24 E, which means that it faces somewhat toward the south, but has been twisted around toward the east through an angle of 24" And he goes on to refer to "N 24 W", S 24 E" and other declination. >From that I inferred (wrongly) that, say a "E 20 N" was plausible. So I was using a declination of 20 when in fact I should be using 70. It would never work, would it? When I say this is Waugh's notation I also presume it is a common notation but since I don't have many books about sundialling I don't know if other authors follow the same convention. I must presume I "invented" the "E 20 N" and "W 20 S" dial and fell in my all trap! I was so mislead by my understanding of how declination was to be measure and used, that when Fer J. de Vries corrected me saying > Do yoy mean a vertcal dial facing north east? Dial N 20 E ? > You wrote E 20 N . > For a vertical dial N 20 E : > the inclination of the plane is 90 degrees and the declination -160 > degrees. I could not understand what he was saying! If he had used less tact with me, perhaps saying "there isn't such a thing as "E 20 N", I could have learned more quickly. Anyway, I think he is too educated to say it. Before finishing this message that is already too long, let me add one more fact that helped to keep me mystified for much longer that it should: the first task I faced was to calculate the N 20 E dial. It worked wonderfully in the first try. When I was in trouble with the other faces I recalcuted it several times and it always worked. I also drew it using the graphical method and it worked the same way. That gave me confidence to apply the formulae the way I was using them. Unfortunately it also made me believe I was calculating the declination in a proper manner. Alas, after all I am a human being. Not only that. As evidence shows, a dumb one! Thank you guys from trying to help me with your silence. I am sure most of you that did not try to help me were just avoiding to embarass me. Some how it worked as a maieutical teaching. - fernando -- Fernando Cabral Padrao iX Sistemas Abertos mailto:[EMAIL PROTECTED] http://www.pix.com.br mailto:[EMAIL PROTECTED] Fone: +55 61 321-2433 Fax: +55 61 225-3082 15º 45' 04.9" S 47º 49' 58.6" W 19º 37' 57.0" S 45º 17' 13.6" W
