Helmut, Yes, there are quadrants with straight hourlines.
In the bulletin of De Zonnewijzerkring nr 10, october 1981 an overview of quadrants is given by Hans de Rijk. He points to: The Horarium Bilimbatum as published in Protomathesus by Fineus Orontius, 1532. This is noted in Bobinger, Alt-Augsburger Kompassmacher, page 50 where you find a small picture of it. A look alike is in the book Orologi Solari van Girolamo Fantoni, page 366. Another quadrant of this type is made by Metz. Here you also see straight azimuth lines in a separate part of the quadrant. As I think to remember such quadrants are correct for noon. The date scale is constructed according the sun's altiudes at noon. For the other hourlines construct correct points for the solstices and just draw the straight line. These hour lines then are aproximations. I think this also is the fact with quadrants with circular hourlines. Construct the correct noon arc and date scale. For other hour lines construct three points for the solstices and equinox. Just draw the arc through these three points. Best wishes, 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: "Helmut Sonderegger" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Saturday, May 31, 2003 10:03 PM Subject: Re: unequal hour lines > Sara, > in my software, which is also on the NASS-repository, I draw quadrants with > temporal hour lines point by point. The circles are aequidistant date lines > (not declination lines itself). The hour lines are evaluated by computing > the day length of the particular days used and then divided by 12. Then the > Sun's altuitude for these hour points is calculated. This method is rather > simple for computers, but in this case I guess no simple formula for the > hour lines can be found. > > The type of the resulting hour lines of course depends on the arrangement of > the arcs for the date lines or declination lines. In old quadrants > aequidistant declination lines are used and then arcs of circles seem to be > used for hour lines. As I do not now any literature about the exactness of > this > construction: Does anybody know such literature? > > It would be an interesting question too if an arrangement of the date lines > can be found where all hour lines become straight lines or at least nearly > straight lines. Does anybody know an answer? > > Helmut > Mail: [EMAIL PROTECTED] > Web: http://webland.lion.cc/vorarlberg/280000/sun.htm > -
