Re:

[Fer J. de Vries]

Hi Noa,   The answers to your questions 1 and 2 may be found at the web site of De Zonnewijzerkring. Address below.   For question 1 follow the links: - calculate and construct - flat sundials/extensive version - secondary procedures and go to pragraph Lines for antique hours or unequal hours. Restriction -66.56 <= phi <= 66.56   The needed formulas are: Calulate half daylength T = arccos( - tan phi * tan decl ) Calculate hourangle t = ( u - 6 ) * T / 6   With these formulas you can covert the antique hour u into local suntime angle t. Correction for longitude and equation of time gives the clock time.   For question 2 follow the links: - article of the month - archives 2003 - month 03-02 how much time is sundial time     Question 3: I don't think the edge of the sun was used to read the time. In antique sundials a shadowpoint was used where to read the time. Such a shadow point can't distiguish between light coming from the edge of the sun and from the center.   Best wishes, Fer.   Fer J. de Vries   De Zonnewijzerkring mailto:[EMAIL PROTECTED] http://www.de-zonnewijzerkring.nl   Home mailto:[EMAIL PROTECTED] http://www.iae.nl/users/ferdv/index-fer.htm Eindhoven, Netherlands lat.  51:30 N      long.  5:30 E ----- Original Message ----- From: Noam Kaplan To: sundial@rrz.uni-koeln.de Sent: Monday, August 09, 2004 4:47 AM Can anyone help me with these questions?   1)  Is there a formula to calculate what time it is on a clock if I know the temporal hour?   2)  Also, why does Waugh write that the sun will never shine on a vertical direct south dial before 6 AM or after 6 PM? If sunrise is at 5 AM wouldn't a shadow be cast on a vertical direct south dial?   3)  On an ancient (Roman and Greek) sundial was noon shown and defined when the edge of the sun cast a shadow on the noon mark or as in later times when the center hit the mark?   Thanks, Noam Kaplan [EMAIL PROTECTED]