Re: On northern vs. southern dials

[Gianni Ferrari]

Anselmo et All, also I  have obtained  to the same conclusions of Fer ( and others)  ( Latitude = 45d) For curiosity I attach the graph of the daily mean number of hours of illumination of the vertical plane at different Latitudes. The plane is illuminated for a period (mean) of 9h 54m,   that is for 3615 hours in the whole year.  There are 4 days in which the plane is illuminated for this period of time :  - when the Sun's Decl. = +15.16d :  May 5 and August 11 (the Sun hiddens behind the vertical plane)  - when the Sun's Decl. = - 15.16d :  February 7 and November 3 (the Sun sets in front of the plane)  More complex is the problem if the plane is declining and not  Southward  Best wishes Gianni Ferrari       Attachment converted: Macintosh HD:Graph1.jpg (JPEG/JVWR) (0003E116)