Hello Mac, I haven't the presize data for the so called Foster Lambert dial at Cambridge, constructed by Gordon Taylor, but the latitude is about 52 degrees. Then the inclination of the plane is 90 - 52 = 38 degrees and the declination is 0 degrees ( facing south ) ( This isn't the equatorial plane!!!! )
This plane is equal with a horizontal plane at latitude 52 - 38 = 14. Construct a so called Foster Lambert dial for this latitude of 14 degrees. One of the 2 styles has an angle to the horizontal plane of 45 + 0.5*14 = 52 degrees. At lat 52 this is a vertical style and that is the trick for this special dial of Gordon Taylor. Hello Dave, On my pages there is one mention of this type of dial. Start at the homepage http://www.iaehv.nl/users/ferdv/ and then follow the links types zonnewijzers andere types hybride zonnewijzer Then you find a drawing of such a dial at lat. 52, incination 45 and declination 0. ( and in the mean time you can learn some Dutch if you like..... ) I used the same scale for the sun's declination and in that case you get 2 different circles for the hourpoints. It is nice to see that the shadow of one style runs clock wise and of the other one anti clock wise. The term hybride is used because one of the possible styles for a horizontal circular dial is just between the vertical line ( as a style on a normal analemmatic dial ) and the polestyle ( parallel to the earth axis ) and the other style has an agle of 90 degrees with the first one. If projecting a circle in the equatorial plane in the direction of such a style onto the horizontal plane you again get a circle and that circle is used for the hourpoints on these dials. Literature: "Equator projection sundials" by Bruno Ernst ( = J.A.F. de Rijk, Netherlands) in Journal of the British astronomical Association 97,1 ( 1986) Also Gordon Taylor has written in this magazin about his dial in number 86,7 ( 1975) Another look to circular dials recently can be found at the WEB pages of Yvon Masse ( French) http://www.union-fin.fr/usr/ymasse/ He doesn't move the style, but draws several circles for different declinations. Call for help !!!!! De Rijk also writes in his article about "central projection sundials" and Yvon Masse has this type described too. The same principle discovered a second time? De Rijk wrote for the first time in 1981/1982 about the "central projection sundials" in the duth bulletin of De Zonnewijzerkring and we don't know of earlier or other sources. If anyone has a reference to this type or has earlier sources, please mention it. Happy dialling to all, Fer de Vries. [EMAIL PROTECTED]
