Hi Luke, I copied your drawing and I am "glad" you made a drawing for a latitude lower then 47 degrees.
I added in red the sun's beam at noon at summer solstice and you may see that the beam is reflected in the wrong direction as John wrote. The grey line between is the normal to the mirror's plane. At higher latitudes this problem disappears, however, at latitudes lower then 47 degrees, some time of the year, a spot of light won't reach the ceiling. Greetings, Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: "Luke Coletti" <[EMAIL PROTECTED]> To: "Anselmo Pérez Serrada" <[EMAIL PROTECTED]> Cc: "Sundial, Mailinglist" <[email protected]> Sent: Sunday, January 06, 2002 6:03 PM Subject: Re: Polar ceiling sundial > > I thought I might share a simple drawing (URL below) that illustrates > Anselmo's idea. In the drawing the Sun is "on" the Equator so the angle > of the Solar rays onto the respective surfaces (polar dial plate and > ceiling) is 90deg. However, it can be seen that this relation holds > throughout the year. The point of the projection disappearing with > southern solar declination values, I think is valid but the extent > should vary. Still, I can't yet imagine how complete coverage can be > practically obtained. Now, I wonder further if a mirrored surface can be > described such that the hour lines are equidistant? I think I know, > anyone have any thoughts? > > > ftp://ftp.gcstudio.com/pub/sundial/ceiling.pdf > > > Regards, > > Luke > Attachment converted: Macintosh HD:ceiling3.gif (GIFf/JVWR) (000398E3)
