Karon, The declination of the sun, north or south to the equator, always is in the range -23.44 to 23.44 degrees.
So make a series of lines on your dial of constant declination, e.g. in steps of 2 or 5 degrees within that range. This will last for ever. Or make a zodiac calendar on your dial with 7 lines with declination of 23.44, 20.15, 11.5, 0, -11.5, -20.15, -23.44 degrees. This sacle also will last for ever. For datelines as in our calendar look for the declination in a astronomical table or so. This is not true for ever because of the effect of the leap year period and longer term effects. For a wanted dateline choose the declination let's say 25 years ahaed and take the middle of the leap year period. Sunrise and sunset on a dial. Make an Oughtred sundial. You directly can read the wanted times for the theoretical horizon. On the sundial it is rather easy to draw (roughly) a silhouette of the surrounding that blocks the sun. 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: karon To: [email protected] Sent: Saturday, August 06, 2011 1:10 PM Subject: Declination lines Ok, I want to see if I have this. the declination lines are designed by laying out a series of circles at different diameters of degrees of arc. Where the circles intersect the hour lines determine the declination arc. When drawing the original dial, the Equinox line is determined as a basis of construction. So, the arc diameter of degrees is determined at the noon line. The number of degrees from the equinox line, up and down, corresponds with the apparent height in the sky of the sun at noon and this determines date. This is how you can mark a particular date on any sundial and mark that as a line just as you would the equinox and solstices. So, where does one find the degrees to use for this measurement? I think I finally have the geometric construction figured out. Now I need to find the numbers for my degrees of movement from equinox. After this, I want to learn how to determine sunrise and sunsets with a dial. Of course, I live in mountains so, it really does not matter to me but I'd love to learn how it is done. Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com ------------------------------------------------------------------------------ --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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