Dear Dialists, So, it looks like Fer de Vries suggestion to use something, his program maybe, to at least be sure of the mirror placement being able to project all the hour lines and declination lines wanted on the ceiling rather than elsewhere is actually a very good idea.
I've never tried this, it hasn't been sunny long enough to make it outside and check this, so far this winter, but it is an idea you can shoot up or down for me. (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. If you then rotated the base of your protractor 90 degrees to be along the east west line and it's upper edge tilted to an angle measured on a piece of cardboard to be the latitude toward the window, couldn't you then by shining the light in from the window determine what hour lines would also be on the ceiling, and if wanted, rotate the mirror slightly to include a favored hour and then fasten it down again? ( each hour line being 15 degrees further from the meridian line ) Then, of course you could construct your hour lines as they occurred with paint or red thumbtacks or however you liked, knowing that the year's efforts would put the lines only where you wanted them. I've heard some strange stories about where some of the hour lines have ended up. (Of course use a protractor made of a non-scratching substance if your mirror is first surface on glass.) Enjoy the light, every minute of it. Edley McKnight [43.126N 123.357W]
