Mac Oglesby <[EMAIL PROTECTED]> writes: > It does leave one surprised that apertures are quite commonly > installed at an angle to the plane receiving the shadow.
Is this irrational or are they just optimizing to some other feature? I mean, what's really so great about circular spots? What you really want is readability, which is a compromise between brightness and blurriness for any pinhole. Assuming you are interested in an accurate reading of the declination as well as the time, the best pinhole may be the usual choice of a circle in a plane perpendicular to the sun's rays (which is itself also a compromise). Extending this logic, a vertically elongated pinhole in a vertical plane might have some advantages over either of the other arrangements. Hmmm. Art
