Dear Dialists,
Oooops! I goofed in a couple of places in my last message on this subject! In using a protractor, it would have to be placed on the level, flat surface next to the mirror, rather than on top of it as I said. The approaches so far mentioned, mine included, seem to assume a mid latitude site. On the equator you would have to have north and south windows and mirrors where I guess you would have to mark the before equinox in one color and after with another. Another approach might be to have the mirror, angled on a pole out from the window to reflect a vertical dial ( a transposed polar dial as per Anselmo Perez Serrada's last posting ) onto a translucent window covering. Not a ceiling dial, but still instructive for students, still markable with maybe stick on stars. > (Assuming penlights and protractors are simple enough technically.) > With a laser pointer or a penlight, a fair sized protractor and a > mirror couldn't you by placing the protractor in the meridian shadow plane > while in contact with the mirror positioned where you want it, then shine > the light in from the window along the angle of latitude first plus > maximum positive declination then minus maximum negative declination and > from the spots shown on ceiling and wall at least tell if the full length > of the analemma of the noon hour would fall fully on the ceiling? ( I > couldn't find an easier way to say this ) Once done couldn't you then > fasten down your mirror. Edley McKnight [43.126N 123.357W] >
