You are right, Dave, not perpendicular to the dial (the sloping plane) but perpendicular to a horizontal plane, thus vertical ( you need a plummet!)
Willy Leenders 50.9 N 5.4 E Dave Bell wrote: > I wasn't sure enough of the maths behind the design, but this sounds > correct. The only thing that bothered me about John's original idea was > tha fact that the (human) gnomon would not be perpendicular to the dial... > > Dave > 37.29N 121.97W > > On Mon, 15 Apr 2002, Willy Leenders wrote: > > > Yes, John, doing so you peoduce the correct drawing for the sloping sundial. > > But you must subtract correctly: 32.5 -3 = 29.5 > > > > An analemmatic sundial is the projection of a sferic equatorial sundial on a > > plane. > > > > In the formulas of Lalande phi is the value of the latitude for the case > > that > > the plane is horizontal (phi is then de angle between the gnonom and the > > horizontal plane). But in general phi is the angle between the gnomon and > > the > > plane on which the projection is done, in your case 29,5 degree. > > > > Willy Leenders > > 50,9 N 5,4 E > > > > mailto:[EMAIL PROTECTED] > > > > John Carmichael wrote: > > > > > Hi All: > > > > > > I have a question. > > > > > > I use the Delta Cad macros to design analemmatics. These macros only > > > permit > > > the design of analemmatics that have flat horizontal faces. But I need to > > > design an analemmatic that is painted on cement that slopes slightly to > > > the > > > south. Let's say the angle of slope is 3 degrees from horizontal and the > > > latitude of the sundial is at 32.5 N.degrees. > > > > > > I thinking that if imput into the DC macro a false latitude of 32.5* - 3* > > > = > > > 31.5 degrees that it would produce the correct drawing for the sloping > > > sundial. > > > > > > Is my thinking correct on this? > > > > > > Thanks anyone > > > > > > John > > > > > > John L. Carmichael Jr. > > > Sundial Sculptures > > > 925 E. Foothills Dr. > > > Tucson Arizona 85718 > > > USA > > > > > > Tel: 520-696-1709 > > > Email: [EMAIL PROTECTED] > > > Website: <http://www.sundialsculptures.com> > > > > > > - > > > > - > > > > - -
