Nicola, In this discussion you write:
"The Planetary hours are equal to the seasonal hours ......" In most of the literature this is true but according to Joseph Drecker (1925) the planetary hours are different from seasonal hours. Drecker defines the planetary hours in his book as the rise of 15 degrees on the ecliptica. He makes a note in his book to a definition by Sacrobosco (around 1230). There are 12 hours in the day and in the night but because a sign rises fast or slow the lenght of each hour is different in the same day too. With my program ZW2000 these planetary hours can be calculted. They look strange and are not so easy to use in practice and rather difficult to construct. Calculation today with computer is easy. So far as I know this timesytem isn't seen on any real sundial. Best wishes, Fer. Fer J. de Vries De Zonnewijzerkring http://www.de-zonnewijzerkring.nl Molens http://www.collsemolen.dse.nl Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: <[EMAIL PROTECTED]> To: "noamk1" <[EMAIL PROTECTED]> Cc: "sundial" <[EMAIL PROTECTED]> Sent: Wednesday, May 16, 2007 9:24 AM Subject: Re:Greek and Roman sundials > You wrote: > > "This is why there is a difference between seasonal and planetary > hours...". > > Where is the difference between seasonal and planetary hours? > The Planetary hours are egual to the seasonal hours and are differently > only for a philosophical and astrological concepts. All treatises of > gnomonica on XVI-XVI-XVIIth century described the Planetary hours only for > the astrological concepts. For this you can see Clavius, Vimercato, > Kircher, etc. > Nicola > > > > > ---------- Initial Header ----------- > >>From : [EMAIL PROTECTED] > To : [EMAIL PROTECTED] > Cc : > Date : Tue, 15 May 2007 22:37:10 +0300 > Subject : Greek and Roman sundials > > > > > > > >> I think my question may not have been clear. What I am interested in >> finding out is >> 1) Greek and roman sundials break up the day into 12 equal parts but the >> amount of time that will pass between each part will not be equal as the >> first and last hour will be longer by approximately 5 minutes due to >> refraction. This is why there is a difference between seasonal and >> planetary hours >> 2) If a Greek or Roman sundial was set up correctly according to what >> they thought was correct, would it actually tell seasonal hours >> accurately or not? >> The part that makes me wonder is the angle of the gnomon. >> >> 3) Is there any formula to calculate what would be the seasonal time on a >> Greek sundial that was accurately set up? >> >> Fred Sawyer gives the formula for the unequal hours >> http://www.sundials.org/publications/dcomp/dcomp2.htm >> >> >> Thanks again, >> Noam Kaplan >> >> >> ----- Original Message ----- >> From: Noam Kaplan >> To: [EMAIL PROTECTED] >> Sent: Tuesday, May 15, 2007 2:25 PM >> Subject: Greek and Roman sundials >> >> >> Does anyone know if the Greek and Roman sundials would in actuality show >> what they are theoretically supposed to show in term of the unequal >> hours? The gnomon was either horizontal or vertical, not on an angle. >> >> >> Thanks, >> Noam Kaplan >> > > > ------------------------------------------------------ > Leggi GRATIS le tue mail con il telefonino i-modeT di Wind > http://i-mode.wind.it/ > > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
