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
