Universal Ring Dial
The Ames Instrument Company Universal Ring Dial
The Ames Instrument Company's universal ring dial is a small but functional, dial available through dealers catering to historical reenactment. It is two-and-a-half inches in diameter and about nine sixty-fourths of an inch thick. Also included is a black leather pouch.
The Ames Instrument Co. Dial Folded Flat
The inner ring features an hour scale with ten minute divisions and opens to form a ninety degree angle with the outer ring. The hours are marked with roman numerals which are somewhat difficult to make out and are apparently acid etched. The outer ring is marked with a latitude scale in one degree increments witch also appear to be acid etched, although the Arabic numerals may be stamped. At the top of the dial is a suspension ring attached to a brass slider which the travels around the circumference of the dial in a pair of grooves allowing the dial's suspension ring to be adjusted for any latitude. The bridge which runs through both rings is marked with a declination scale and there is a sliding cursor (gnomon) which can be set to the appropriate position for the current time of year.
To use the dial you adjust the suspension ring slider to your latitude and slide the declination cursor to the correct declination for the time of year. (Roughly speaking, declination is how high the sun appears in the sky as measured from its average position. The sun is highest in the summer, lowest in the winter and in the middle during the two solstices. You will have to look up the declination in an almanac, for example). Open the dial and suspend it by its ring, then rotate the dial until a spot of sunlight falls through the hole in the cursor on the inner circumference of the inner ring. The hour scale tells you Local Apparent Time.
Close Up of Right Angle Stop on Opened Dial
The Ames Instrument Company's universal ring dial's chief recommendation is its reasonable cost and ease of availability. The dial is functional though somewhat workman like in appearance and finish. The small size makes the dial quite practical for carrying with you; however, the etching of the hour scale is a little hard to read. Additionally, the thickness of the brass rings actually makes it a bit difficult to use the dial in the days near the equinoxes and during the hours close to noon because the rings block the sunlight from shining through the hole in the declination cursor.
I have no connection with Ames Instrument Company. My comments on this dial are strictly my personal opinion. If you are interested in a universal ring dial by all means see one of the models I have reviewed for yourself and form your own opinion. The Ames Instrument Company has a good looking new website at http://www.amesinstrumentcompany.com (4/14/97).
If you have questions or comments please e-mail me at ghhcom@aol.com.