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 ----- Original Message ----- From: "Sara Schechner" <[EMAIL PROTECTED]> To: <sundial@rrz.uni-koeln.de> Sent: Thursday, May 29, 2003 2:55 PM Subject: unequal hour lines > Hi, > I am working on a project that involves the traditional unequal hour lines > (also known as seasonal and temporal hours) on a horary quadrant and an > astrolabe. In other words, I want to get the right arcs for use on an > instrument that measures altitude of the sun and makes use of a solar > declination scale along the radius of the instrument. These arcs would be > latitude specific, as on traditional instruments. > > What techniques have list members found to construct them? Do you use data > points plotted? geometric construction? > > Thanks for the advice and input!! > > Happy Dialing, > Sara > 42.38 N, 71.13 W > Sara Schechner, Ph.D. > David P. Wheatland Curator > Collection of Historical Scientific Instruments > Harvard University, Science Center B-6 > 1 Oxford Street, Cambridge MA 02138 > 617-496-9542 (Tel) > 617-496-5932 (Fax) > > - > -
