Andrew James <[EMAIL PROTECTED]> writes: > 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?
I'll buy it. I did a lot of thinking and some experimentation last summer. I used a slit and two pinholes and tried to balance the intensity of light on the two sides. I found I could judge the moment of symmetry within a second or two of time, which corresponds to one arc minute or better of angle, which I found very respectable. The principles are these: (1) your eye can judge symmetry better than just about anything else, and (2) the light passing through lenses/pinholes/slits varies most sensitively if the apparatus is aligned with the limb of the sun. My slit produced a line image of the sun. Both the diameter and the separation of my pinholes were about equal to the width of this line image. --Art
