Fernando Cabral wrote: > > Hello sundiallers > > I am calculating my first real sundial. I am more nervous than a > father expecting to see his first newborn. > > Latitude is 15 45' 44.4" S, Longitude is 47 49' 40.1" W > > It is a horizontal sundial. Its dial plate (is it better to say dial > plate or dial table, or whatever?) has a diameter of 3000mm. The angles > I've calculated, starting from the noon line are (using Angle = atan > (sen LATITUDE * tan HourAngle)): > > 2,048 4,163 6,419 8,913 11,774 15,197 19,494 > 25,196 33,256 45,392 64,142 90 > > (Americans, please replace the comma with a dot). > > I've checked this at least 5 times so I don't expect any troubles here > (unless I've been using wrong formulae). > > Than I designed a gnomon with an angle of LATITUDE (15,762), pointing > South, with a lenght of 1388 mm. > I chose this lenght because I expect its shadow to be 1500 mm long in > our winter Solstice for our > hemisphere (June 21). > > According to my calculations, in the Summer Solstice the shadow lenght > will be 1284,576 mm and > when the Sun is crossing the Zenith here in Brasilia shadown lenght will > be 1335,808 mm. > > First question is: do these figures look OK? > > Second question is: if I want to include a line marking some special > date such as a birthday > how do I calculate the parabola the tip of the shadown will describe in > that particular day? > > Sorry for this long message with so many novice questions. And thank you > for your attention. > > - fernando > > -- > mailto:[EMAIL PROTECTED] http://www.pix.com.br > Fernando Cabral Padrao iX Sistemas Abertos > > [EMAIL PROTECTED] [EMAIL PROTECTED] > Fone: +55 61 321-2433 Fax: +55 61 225-3082
Hi Fernando, The angles for the hourlines are correct. The distance along the noon line to the point of juni 21 isn't correct. It should be about 1643 in stead of 1500. Your other distances are corect. See the attached image. To calculate date lines download my computerprogram at http://www.iaehv.nl/users/ferdv/ Fer de Vries. Attachment converted: MAC Hard Disk:image1.gif 1 (GIFf/JVWR) (00009B51)
