Ciao a tutti! I would like to suggest a simple way to measure the declination of a wall.
I fix a strip of mirror (say 3cm high 10 cm wide) horizontally to the wall by means of adhesive tape. Then I suspend vertically in front of it, and about 10 cm apart, a long strip of glass (say 20-30 cm high, 3cm wide) to which I have applied longitudinally two parallel strips of black adhesive tape in such a way to leave between them a slot of 2-3 mm. (all measures are indicative, experience can teach the best) When the sun is just in front of the wall the solar ray passing through the slot hits the mirror and the reflected ray passes through the slot again. I can realize that by collecting the reflected ray on a piece of paper. As the event takes a few seconds, I take the beginning and the ending times to calculate the mean time. From that time I can calculate the azimuth of the wall. Substantially I have converted an angle measure to a (hopefully) more precise measure of time. The method is simple, but it suffers from many disadvantages: you can take just one measure per day and just when the sun is in front of the wall (malicious clouds permitting), when the sun is very high in the sky you may need a very long strip of glass, which should be kept firmly strictly vertical. Ciao Angelo --- 44 32' 10''N 11 32' 15''E ---
