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Sundial Hour Lines Lay out

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LAYING OUT THE SUNDIAL HOUR LINES - Page 9

This sundial must be placed in a perfectly vertical position, so that the substyle line lies in the plane of the meridian and the face of the sundial looks to the true north point of the horizon. THE DIRECT EAST AND WEST VERTICAL SUNDIALS; The planes of the direct east and west vertical sundials lie in the plane of the meridian, and for this reason they are some-times referred to as meridian sundials. The hour lines for each sundial are calculated in exactly the same way, so it is necessary only to describe the construction of one of them. The diagram shows the construction of the hour lines for the east sundial, in latitude 5a°3o'N. The GNOMON is usually made in d.e form of a flat rectangular bar, or in the shape of a pin. It is perpendicular f to the face of the vial. The STYLE points to the celestial pole and is parallel to the sundial plate. The SUBSTYLE is the 6 a.m. line (the 6 p.m. line in the west sundial) and points to the celestial pole. The HEIGHT OF THE STYLE is measured in inches (or millimeters) and is determined by the size of the sundial plate. It is usually from a/ to 3 inches in height. The HOUR LINES are parallel to the substyle. The Construction: Draw the horizontal line AC. This represents the plane of the horizon.

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