Dear Thierry and membership, I've heard recently a number of stories about college professors and various book dials they have made. Quite simple and rather sneaky.
The stories have been of several colleges and several professors, so perhaps it is wide spread, or just college folklore. Just about any real book with quite noticeable curves around the spline opening or any dial constructed to resemble same can have polar hour lines put upon it in a simple way. The stories mention a penlight, a protractor, a pencil lead, a clamp or tape, a light blue pencil or technical pen with very dilute blue ink, a pair of rose colored sunglasses, a straightedge, and the metal framework of a treadmill. They also mention a bookrest that is doubly hinged, an outdoor table and orientation marks. The penlight is fastened to the upper rail of the treadmill with the clamp or tape. The book is opened directly below the light, a small support for the protractor is made or found that aligns to the same height as the bottom of the open spline of the book. The protractor is tested by sliding a pencil lead over the outer markings til the shadow crosses the center of the protractor. the protractor is slid the 90 degree mark is centered by this test. the book is slid til it is aligned with the center of the protractor. This is the noon mark and should fully light the book. The light is slid til it shows as 15 degrees on the protractor and the shadow of one book curve is on the other book curve. a ruler and a light blue marker mark out the edge of this shadow as the first hour from noon. The light is moved in 15 degree steps and the other lines marked both before and after noon. Multiple pages could be marked by just flipping the pages before marking. This book is set up outside on a two hinge book rest. The top hinge sets the book spline to be parallel to the earth's axis when the book rest is facing south, the second hinge at the side rotates the book around the spline to compensate for time differences. The rose colored sunglasses are used to protect the eyes and make the light blue markings show up. While reading away, the professor can tell the time within a few minutes without even looking up. Enjoy the Light! Edley McKnight [43.126N 123.357W]
