SUNDIAL SECTIONS:

Sundials Home

History of Sundials

Why the Sun Dial keeps time

Developing and Making Sundials

Sundial Materials

Sundial Hour Lines Lay out

Sundial "Furniture"

Declination Lines of Sundials

Portable Sundials

Interesting Sundials of the World

DECLINATION LINES OF SUNDIALS - Page 8

The Construction The equinoctial line, is drawn through the foot of the perpendicular style at right angles to the 6 o'clock line. The horizontal line AB is drawn through the point where the equinoctial line cuts the 6 o'clock line and through the foot of the perpendicular style, which on this sundial are coincident, at F. The line AB makes an angle with the hour lines equal to the latitude of the place (in this case 400). In Figure 2, the line F'E' represents the equinoctial line; through F' draw F'ix making an angle with F'E' equal to the greatest northern declination of the sun (23°27'). Lay off from F' the distance F'N' equal to the height of the style. Take the distances from N to a, b, c, d (the points where the equinoctial cuts the various hour lines), and lay these distances off on F'E' from F' to a', b', c', Through the points N', a', b',... draw lines perpendicular to F'E', cutting the line F'ii at 6, 7, 8, 9, 10, II, (the figures represent the corresponding hour lines in Fig. I). Lay off the distances N'6, a'7, b'8... so that F6 = N'6, a7 = a'7, b8 = b'8,.... Then, a line drawn through the points 6, 7, 8, 9, 10, II, will show the path of the shadow cast by the nodus when the sun reaches its greatest northern declination. To find the points, on the hours before 6, through which the line of declination is to be drawn, make k5 and mq equal to a'7 and b'8 respectively. In the same manner all other lines of declination can be plotted on the sundial plate. A west sundial for the same latitude will be seen, with its lines of declination. The morning hours will become the afternoon hours, and the horizontal line will show the time of sunset. Sunrise and Sunset By combining the east and west sundials, the time of sunrise and sunset may be estimated, throughout the year. The ac-curacy depends somewhat upon the size of the sundial, and more so upon the careful laying out of the lines of declination and the horizontal line.

  more on the declination lines of sundials..