Hi John, Indeed, this is a simplification of the formula for a sundial.
In stead of phi I prefer another letter for the style height but that's just a choice. I use v. Phi then still is the latitude. It also is my practice to start with the calculation of the styleheight for any planar sundial. I take care of the right sign which tells me if the equivalent horizontal dial is at northern or southern latitude. I then know if the hourlines run clockwise or anticlockwise or are parallel. I also know if the polestyle points to the north or south poleor is parallel to the sundial's plane. If you also calculate the hourangle of the substyle (ts as I use) the formula for any dial is: tan z = tan ( t - ts ) * sin v. This is the simplification as you propose but now for any planar dial. You can read more about this at our website at http://www.de-zonnewijzerkring.nl/eng Follow the links Calculate and construct Extensive version. Look at the paragraph notes and how the program ZW2000 uses this principle. 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: sundial@uni-koeln.de Sent: Tuesday, September 04, 2007 1:05 AM Subject: A simpler statement? According to various books, one lays out the hour-line angles of a horizontal dial for the latitude, one lays out the hour-line angles of a direct-south vertical dial for the co-latitude, and one lays out the hour-line angles of a reclining direct-south dial for the co-latitude minus the angle of reclination. I wonder if it would be simpler to say (for northern latitudes) that: 1) The style of the gnomon always points to the (ideal) north star 2) Hour-line angles are laid out by D = ARCTAN (TAN t * SIN phi) where D = hour-line angle t = solar hour angle phi = angle of style to dial plate This is the usual equation, but I have redefined phi. John B ------------------------------------------------------------------------------ Email and AIM finally together. You've gotta check out free AOL Mail! ------------------------------------------------------------------------------ --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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