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LAYING OUT THE SUNDIAL HOUR LINES - Page 7

Also draw a line from A through the point L. These lines will be those required for the morning hours. To obtain the afternoon hour lines, extend the line FA to G, making AG equal to AC. Draw CG and continue the construction as shown above. shows the hour lines transferred to the sundial plate, and the way in which they should be numbered. FIGURE 3 shows the position of the sundial when in use. Hour Limitations The sun will not shine upon this sundial before 6 in the morning or after 6 in the evening; therefore it is necessary to show only those hours between 6 a.m. and 6 p.m. Setting the Sundial This sundial must be placed in a perfectly vertical position, so that the 12 o'clock line will lie in the plane of the meridian, and the plane of the sundial will face due south, or lie in the plane of the prime vertical. See also Section V. THE NORTH VERTICAL SUNDIAL The plane of the north vertical sundial is perpendicular to the plane of the horizon and faces the true north. The diagram shows the construction of the hour lines for latitude 48°3o'N. The STYLE points to the celestial pole. The SUBSTYLE is the 12 o'clock line and lies in the plane of the meridian. The HEIGHT OF THE STYLE is equal to the complement of the latitude, which in this case is 41°30' (90°- 48°30 = 41°30').

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