Tony Moss suggested using a non-diverging sunray after passing between pairs of posts 0.4mm apart for a heliochronometer.
Art Carlson wrote: <snip> But this line is not unique. You will get such a line if the instrument is aligned toward any part of the sun's disk. <end> My idea is this: is it possible to combine the two points made? Arrange, say, two sets each of four posts with three 0.4 mm gaps between, one set having slightly wider posts but with the same gap, so as to make three light rays the outer two of which diverge by the same small amount - say 0.2 degrees - in each direction from the inner. Then balancing the appearance of the outer rays should give a rather more accurate estimation of the angle of the centre of the solar disc. Any takers? Regards Andrew James
