With any conventional horizontal, reclining, vertical or equatorial sundial the gnomon is parallel to the earth's axis, regardless of the shape and orientation of the dial. This is clearly shown by polyhedral sundials, where every face's gnomon is parallel to each of the others. And it is indeed true that the angle between the gnomon and the vertical is equal to your co-latitude. So, if you have been making declining dials with gnomons that are not, you have been making them inaccurately. (Exceptions to the rule that the gnomon be parallel to the earth's axis include analemmatic dials, where it is vertical, and Foster-Lambert dials, including those described by Yvon Masse, where it can be of any orientation.)
One quick way to verify a declining vertical dial is to construct a temporary horizontal dial nearby. Are the gnomons parallel? They should be. Regards Chris ======================================================= Chris Lusby Taylor Tel: 44 (0) 118 924 6236 Oracle Corporation UK Limited Fax: 44 (0) 118 924 5561 Email: [EMAIL PROTECTED] (Formerly [EMAIL PROTECTED]) ======================================================= The statements and opinions expressed here are my own and do not necessarily represent those of Oracle Corporation. Date: 24 Nov 98 10:42:07 From: Fernando Cabral <[EMAIL PROTECTED]> To: "[email protected]" <[email protected]> Subject: Style angle on declining sundials Reply-to: UKUNIX2.UK.ORACLE.COM:[EMAIL PROTECTED] Return-Path: <[EMAIL PROTECTED]> Received: from mail-gw3.uk.oracle.com by uks447 (SMI-8.6/SMI-SVR4) id SAA27206; Tue, 24 Nov 1998 18:48:49 GMT Received: from uksn98.uk.oracle.com (uksn98.uk.oracle.com [138.3.208.67]) by mail-gw3.uk.oracle.com (8.9.1/8.9.1) with SMTP id SAA25954 for <[EMAIL PROTECTED]>; Tue, 24 Nov 1998 18:48:49 GMT Received: from mail1.rrz.Uni-Koeln.DE ([134.95.19.28]) by uksn98.uk.oracle.com via smtpd (for ukaa04.uk.oracle.com [138.3.208.99]) with SMTP; 24 Nov 1998 18:48:49 UT Received: (from [EMAIL PROTECTED]) by mail1.rrz.Uni-Koeln.DE (8.9.1a/8.9.1) id PAA08277 for sundial-out; Tue, 24 Nov 1998 15:45:43 +0100 (MET) Received: from boemia.pix.com.br (boemia.pix.com.br [200.239.61.10]) by mail1.rrz.Uni-Koeln.DE (8.9.1a/8.9.1) with ESMTP id PAA08237 for <[email protected]>; Tue, 24 Nov 1998 15:45:35 +0100 (MET) Received: from pix.com.br (fernando.pix.com.br [200.239.61.19]) by boemia.pix.com.br (8.8.5/SCA-6.6) with ESMTP id PAA04843 for <[email protected]>; Tue, 24 Nov 1998 15:44:36 GMT Message-ID: <[EMAIL PROTECTED]> Organization: Padrco iX - http://www.pix.com.br X-MIME-Autoconverted: from quoted-printable to 8bit by mail1.rrz.Uni-Koeln.DE id PAA08272 Sender: [EMAIL PROTECTED] Precedence: bulk X-MIME-Autoconverted: from 8bit to quoted-printable by mail1.rrz.Uni-Koeln.DE id PAA08277 MIME-Version: 1.0 Content-Type: text/plain René R. J. Rohr, in his "Sundials - History, Theory, and Practice", page 55 says about how to place the style in a declining dial: "The principle is simple. The style lies in the plane of the meridian and its axis makes with the vertical of noon an angle equal to the complement of the latitude". In the four decliners I built ballpark measures (I didn't have the instruments to take a proper measure) indicate he is right about the plane of the meridian. As to the the angle its axis makes with the vertical, it does not match what I've found. Am I wrong again? - fernando -- Fernando Cabral Padrao iX Sistemas Abertos mailto:[EMAIL PROTECTED] http://www.pix.com.br mailto:[EMAIL PROTECTED] Fone: +55 61 321-2433 Fax: +55 61 225-3082 15º 45' 04.9" S 47º 49' 58.6" W 19º 37' 57.0" S 45º 17' 13.6" W
