> Following on from Rolf Menzl's message, can anyone tell me if there is a > way of determining the declination of a wall RAPIDLY with a single reading > AT ANY TIME OF THE DAY ? > The method to find true north using a horizontal board with a vertical > gnomon, whereby measurements are made either side of noon and the positions
What I did was the following: The shadow of a vertical gnomon (in fact a cord with a lead) casted on a horizontal board (checked by a spirit-level). The board was aligned to the wall of which the declination should be measured. Then I just marked the shadow and wrote down the exact time. By this I calculated the orientation of the wall relative to the azimuth of the sun. If I now calculate the suns azimuth at the time and date when I marked the shadow I can derive the declination of the wall just by subtracting two angles. The suns azimuth can be calculated by means of formulae given in various books, e.g. Jean Meeus, Astronomical Algorithms or Oliver Montenbruck, Thomas Pfleger, Astronomy with the PC. I've made a program for my pocket calculator HP 28S which makes it quite easy to calculate the suns azimuth (and elevation) on the spot.
