Hello Mike, Let the arms and the top 'stub' all have length L. The cross lies in the equatorial plane, so that the sun is at most 23.5 degrees out of that plane. The maximum distance from each pole-style to the corresponding face is from one corner to the next, hence L*V2 . The shadow is at most L*V2*tan(23.5) = 0.62 L out of the plane there.
L being 400 mm in your case, the minimum depth is about 250 mm for the shadow of the edge to stay within the dial face. By the way, only recently did I realize that the cross dial consists of polar dials and direct east and west vertical dials. Regards, Frans --------------------------------------- From: "The Shaws" <[EMAIL PROTECTED]> To: "Sundial, List" <[email protected]> Subject: Cross dial Date sent: Mon, 19 Feb 2001 17:52:28 -0000 > I have been asked to asssist in the replacement of a cross dial. > The cross has each of the four "arms" the same length, 400mm. > How "deep" does each arm have to be, (i.e. ratio of length to depth) so > the shadow of each style is still visible at maximum declination, and > still have enough left to be able to read. Most of the books talk of each > arm being a cube, but that isn't really practical in this case. > > Help appreciated > > Mike Shaw > > Wirral, UK > 53' 22" N > 03' 02" W ===================================== Frans W. Maes Peize, The Netherlands 53.1 N, 6.5 E www.biol.rug.nl/maes/ =====================================
