Dear Frans, I visited your website yesterday and think it is great. Really nice images!
With respect to the question of classification of sundials raised by Fritz and yourself, it seems to me that this picks up on the topic of sundial taxonomy that was discussed on the list in February. In case you missed it, I will copy my classification system below. I use this method to delineate what might be called a "natural history" of sundials with genera, species, and familes. Like any system of taxomony, there are many ways that it can be done. Rather than divide the world into the "genera" of nodal and pole-style dials (i.e., of whether we are projecting a point or a line onto the hour scale), I prefer as my main classes the parameter of the sun's motion that we are using. The sun's apparent motion, being basically an astronomical relationship between the earth and sun, seems to me to be more fundamental than the gnomon. But that is my personal preference, and the one I use in my cataloguing of historical sundials at the Adler Planetarium and Astronomy Museum, and elsewhere. Here is what I wrote in February 2000. It gives my general principles. If people would like to comment on a specific breakdown of types, I can post that later. >>>>>> 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 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 39:02 N 77:01 W ------------------------------------------------------- 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]
