I looked up 'heliochronometer' and 'solar chronometer' in the index of Cousins' 1970 book (Sundials - The Art and Science of Gnomonics). It seems he accepts the makers' term - if you call your sundial a chronometer, then Cousins would happily use the same term. There are three such in the book.
One is the Pilkington and Gibbs mechanical equinoctial, which uses a kidney-shaped adjuster to show mean time. It has a vernier minute scale. The second is a portable equinoctial with a polar-mounted telescope geared to the hands of a watch. As far as I can see it has no adjustment for the equation of time, but it does read minutes. The third is an equatorial sundial with a cylindrical dial marked with half the analemma. It therefore reads mean time, but is so small it could not be read to the minute. Nor does it have any vernier or transversals to suggest that it could be read to the minute. So there seems to be no unifying feature - neither a minute scale nor mean time. Since, in the past, many sundials' primary function was to regulate clocks, I don't think this distinguishes a chronometer. For a Swiss watch to be called a chronometer I believe it has to pass tests for accuracy in various positions and temperatures. I would be happy to call a sundial a chronometer if it could be read to the minute and bore an equation table or built-in mean time display. Regards Chris ======================================================= Chris Lusby Taylor Email: [EMAIL PROTECTED] (Formerly [EMAIL PROTECTED]) =======================================================
