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Sundial Hour Lines Lay out

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Declination Lines of Sundials

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Interesting Sundials of the World

LAYING OUT THE SUNDIAL HOUR LINES - Page 23

These two points are called the north and south poles of the ecliptic. The north and south polar circles are noted by the lines WR and KY, drawn through W and K, parallel to the equator. The Equinoctial Colure is indicated by the line SCN. It passes through the points where the ecliptic crosses the equator, and the north and south poles of the sphere. The plane of the Solstitial Colure is perpendicular to the plane of the equinoctial colure and it passes through the poles of the sphere, the zenith, and the nadir. In the diagram it coincides with the meridian, shown by the circle SENA. The Armillary as a Sundial The SUNDIAL PLATE will be the inner surface of the ring representing the Equator. The GNOMON is a thin round rod, extending through the sphere as SCN, and lies parallel to the axis of the earth. The STYLE is essentially the gnomon, unless it is quite large in diameter. It lies parallel to the earth's axis and points to the celestial pole. The SUBSTYLE is the 12 o'clock line. The HEIGHT OF THE STYLE. In this case it is the angular distance of the style above the plane of the horizon, which is equal to the latitude of the place. The hour lines are easily constructed. The method is the same as that for the equatorial sundial shown on page 96. Beginning at the point A, which represents the intersection of the equator and meridian, mark off equal spaces of 15 ° each on the sundial plate. Thus will the morning hours be laid out on the west side of the sphere and afternoon hours on the east side.

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