Hi Everyone, I too have been watching the discussion on so-called azimuth sundials and have been concerned about the confusion in terminology. I want to second remarks made by Gianni Ferrari and John Davis.
I think it is useful to divide sundials into major classes based on what parameters of the sun's motion are being used to measure the time. Such classes would include hour-angle, azimuth, altitude, and combinations. Particular types within each major class are then identified by the orientation of the hour plate (e.g., horizontal, vertical, declining, inclining, equatorial, polar, or other aspects of the surface on which the hour lines are projected), the nature of the gnomon (e.g., string-gnomon, pin-gnomon, etc), whether the instrument is particular or universal (i.e. for a set latitude or adjustable for multiple latitudes), whether it is fixed or portable, and other special characteristics that distinguish particular forms (as in the case of a cannon sundial, compass sundial, floating sundial, polyhedral sundial, diptych, magnetic azimuth dial, universal ring dial, etc). When there are many examples of a particular type that share historical characteristics of time and place of origin (e.g., Augsburg-type) or debt to an important designer (e.g. Butterfield-type, Oughtred-type, Regiomontanus-type, de Rojas-type), these are given special names. But these special names should be used sparingly. Lastly, one needs to specify what the dial is indicating. This may include hours (common, Babylonian, Italian, mean, etc), seasons or calendar dates, solar declination, sun's position in the ecliptic, lengths of daylight or darkness, and so forth. The information displayed does not alter the class of the instrument and only rarely distinguishes one type from another. I would also like to urge us to use the traditional names where they exist and not invent or use new names. I know I'm preaching to the choir here, but let me go on record as saying that I think it is causes public confusion for marketers (with all due respect) to rename ring dials as aquitaine dials, armillary/equatorial dials as explorer dials, and so forth. Cheers, Sara ------------------------------------------------------- Sara Schechner, Ph.D. Center for History of Physics American Institute of Physics 1 Physics Ellipse College Park, MD 20740 Tel: 301-209-3166 / Fax: 301-209-0841 [EMAIL PROTECTED] Gnomon Research __Curators on Call __Outreach Adventures 1142 Loxford Terrace Silver Spring, MD 20901 Tel/Fax: 301-593-2626 http://www.wam.umd.edu/~sschech [EMAIL PROTECTED]
