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> > > > > - > > - > -
