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This model gets around this problem using a light pointer created by a CD (actually two are needed, one on each face of the dial) that replaces the shadow of the gnomon during the days around the equinoxes.
Pass: rainer
The EQUATORIAL SUNDIAL is the easiest dial to make. In its simplest form it consists of a round disk with a rod (the gnomon) through its center. The scale is linear with hour markers every 15 degrees.
(See http://www.sundials.co.uk/projects.htm)
The gnomon must be aligned parallel to the earth's axis and therefore point exactly            . The disk has to be parallel to the Earth's equatorial plane. That requires the the gnomon's angle with the horizontal to be equal to the local latitude.
Normal equatorial sundials have one limitation though; they do not work well when the sun is on the celestial equator, i.e. during the equinoxes, because the sun's light falls on the edge of the dial plate.