Re: Book by Cousins

[fer j. de vries]

Hello Anselmo,   Unequal hour: If you devide the time between sunrise and sunset by 12 you get  the unequal or antique hour. In the course of a year the length of a day between sunrise and sunset varies and by that also the hour varies, but in one day the hours are equal.   Canonical hour: Draw half a circle on a south facing vertical plane and devide the circle in 12 ( or 8 or 6 ) parts and then you have a dial with the canonical hours. A rod perpendicular to the wall is used to produce the shadow line to read the dial.   Planetary hour:  In literature antique hours often are named planetary hours and then there is no difference between these types. However, according to Joseph Drecker, a German scolar, planetary hours are quit different. He wrote about this in 1925, based on a definition by Sacrobosco:   hora naturalis est spatium temporis in quo medietas signi peroritur. ( footnote in Drecker's book )   At sunrise the first hour starts, just as for antique hours. If 15 degrees of the ecliptic has risen, the second hour starts and so on. Because the rise of a sign of the ecliptic ( 30 degrees = 2 hours ) is very irrigular an hour varies also very irrigular, not only in the course of a year, but also in one day. There are always 6 signs ( is 180 degrees ) above the horizon so between sunrise and sunset there are always 12 hours, just as for the antique hours.   Hope these notes are of help to you.   Best wishes, Fer.   PS: With my program Zw2000 you may calculate planetary hous for any plane.     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: Anselmo PÈrez Serrada To: fer j. de vries Cc: Sundial, Mailinglist Sent: Saturday, November 17, 2001 9:12 PM Subject: Re: Book by Cousins Hi, diallers!   Just a question and a nice motto I heard on the TV:   The question is: can anybody tell me which is the difference between unequal hours, canonical (ecclesiastical) hours and (this is more difficult, I think) planetary hours?   And the motto is:                        So as nostalgia, I just show you but bright hours.   Best wishes,             Anselmo Perez Serrada            [  41.63 N   4.73 W ]