Sara, For sundials, although not your question, I calculate antique hourlines point by point. Then it's good to see that at higher latitudes the lines aren't straight lines.
For a tympan of an astrolabium I draw them as arcs by deviding the daylight parts of the solstice circles and equinox circle in 12 parts. So I find three points to draw each hour arc. On the dorsum af an astrolabium often a famous circular construction for antique hours is found, however, not correct for times other then at the solstices and equinoxes. For a quadrant I never have constructed the antique hourlines. I did construct such lines in a nomogram as done by Peter Apian or Johann Stab and others as you may read in Compendium vol.5 nr. 4 december 1998. There the line representing the daylight part is devided in 6 equal parts. In the book by Joseph Drecker, Die Theorie der Sonnenuhren, 1925, you may find analytical formulae for the antique hourlines but not practical for use in construction of a sundial, quadrant or astrolabium. I hope this is of help to you. Best wishes, Fer. 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: "Sara Schechner" <[EMAIL PROTECTED]> To: <[email protected]> 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) > > - > -
