Selecting the Right Sundial

The selection of the right sundial depends on your individual artistic tastes, the degree of accuracy you require, the suitable locations available to you for setting out your dial, and the amount of money you want to spend. Unfortunately, finding a good sundial in a store may be next to impossible. You will probably have to have your dial custom-made. First of all, the location of the sundial obviously must receive full or filtered sun most of the day. Decide what type of sundial fits this space (analemmatica dial that uses the altitude
rather than the azimuth of
the sun for indicating time, horizontala dial designed to be
installed laying flat on a
horizontal plane, polara dial polar-aligned to latitudes
+90º (N) and -90º (S), heliochronometera precise sundial that shows
Standard (watch) Time directly, or monumentala very large, public sundial). Then determine what you want to spend, and the accuracy desired. Generally, as precision increases, the dial must be larger, and consequently, more expensive. Finally, determine which artistic style suits your tastes and location.

You must try to find a sundial that was designed to be placed in or near the city or place in which it will be located. For a sundial to function properly, the dial maker must know its latitude and longitude. (Personally, I would never buy a sundial that doesn't have the proper coordinates stamped somewhere on it). For each degree of longitude that the dial is moved from its designated location, there will be a four-minute error. For example, if you buy a sundial made for Roswell, New Mexico, at longitude 105° W. and place it in Tucson, Arizona at 111° W., it can be off by about 24 minutes. My sundials are corrected for longitude and do not have this problem. You should be within the ballpark if you locate your sundial anywhere within or near the city for which it was designed.

Accuracy is further compromised if the sundial is made for the wrong latitude or is poorly constructed. Beware of cast bronze sundials with raised hour lines because they distort the shadow. Cast bronze and ceramic store-bought sundials are usually mass-produced. These sundials will not tell time correctly because they are not designed for the user's location. Also, light-colored dial faces show the shadow better than dark colors. The bronze store-bought dials usually have black faces! Before purchasing a store-bought sundial, check the gnomon to make sure it is sturdy, doesn't wobble, and has a sharp, perfectly straight edge. You should also measure the angle the gnomon makes with the dial face using a simple protractor. On a horizontal dial this angle should be equal to your latitude.