NauticalMart Armillary Sphere Globe 5" Nautical Brass Compass

 

This Armillary Sphere measures 6 inches tall, 3 1/2 inches diameter
 
The armillary is an ancient astronomical instrument used to track date, time and various celestial happenings throughout the year. In a simplified version it is also known as the sundial. The armillary sundial differs from the garden sundial in that it is three-dimensional in its presentation and is more accurate when giving time. It has a fixed gnomon style that is aligned with the Earth's rotational axis and a spherical shadow-receiving surface that is aligned equidistant from the axis. In order for the armillary to be used accurately it must be positioned properly. Once this is done, reading the armillary is accomplished by simply locating the edge of the shadow cast by the gnomon style on the shadow-receiving surface and noting the numerical and graduated hatch marks.