Roger Bailey wrote: > > You were right. There are lots of us on this mailing list. Sundial design > and celestial navigation use the same math, spherical trigonometry. > > The usual equation for altitude is: > Sin Hc = Sin Lat X Sin Dec + Cos Lat X Cos Dec X Cos t. > > If you want azimuth: Sin Z = Sin t X Cos dec / Cos Hc. > > My reference is Bowdich, "American Practical Navigator" > > I've plugged these formulae into lots of programmable calculators. Once you > have put the formula in once, the program is there, ready for use. > > I've had fun with the special case of this formula, when Hc = 0. > Cos t = - Tan Lat / Tan Dec can be solved for the local time of sunrise and > sunset (ignoring semidiameter and refraction). < snip...
The last formula should be Cos t = - Tan Lat * Tan Dec. Not / Fer de Vries.
