Diallists, In my message of 2002-01-09 about the limits of a polar dial on a ceiling I ended with:
+ADw- Who has an inclined ceiling, higher at the south end? +ADw- Won't that be better? I wanted to know this for sure and I started with a ceiling with an inclination of 160 degrees in stead of 180 degrees. A difference of 20 degrees as is shown in the attached picture. The mirror now gets an inclination of 0.5 ( phi - 20 ). For latitude 52 this is 16 degrees. The pattern on the now inclined ceiling also is a polar dial. I did not look for the extreme limits, but just gave it a chance. Following the same procedure the polar dial is cut off at about 3.5 hours before and after noon and it is seen that the mirror is less inside. (distance CB ). At the left the pattern for a south facing dial though CM with (pin)gnomon CB is drawn. The mirror is at distance CM from C and that is shown with the line KL. At summer solstice the mirror will be in the shadow of the edge of the ceiling untill about 3.5 hours before noon and is shaded again 3.5 hours after noon. So this configuration will work 7 hours at summer solstice. A great improvement compared with an horizontal ceiling. I only need to rebuild my house............. Best wishes, Fer. Fer J. de Vries ferdv+AEA-iae.nl http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E Attachment converted: Macintosh HD:ceiling5.gif (GIFf/JVWR) (00039FCA)
