A Fairfax County Public Schools Planetarium
How to Set Up & Use a Horizontal Sundial
Finding the Direction of True North
For more information, visit the How to set up a horizontal sundial Web page: http://www.sundials.co.uk/setup.htm
Visit the SCSA Equatorial Sundials Web page for an explanation of how the sundial may be used to align itself with your local meridian: http://www.wsanford.com/~wsanford/exo/sundials/equatorial_sundials.html#setting-the-dial
Find your meridian by using a self-orienting Combination Analemmatic-Horizontal Sundial: http://www.wsanford.com/~wsanford/exo/sundials/shadows.html#combo-sundial
Telling Time Using the Sundial
Morning times appear on the dial face to the left side of the meridian; afternoon times to the right. Most days, Solar Time and Standard Time are slightly different (by as much as 16 minutes). This time difference is known as the Equation of Time. Add or subtract the Equation of Time as appropriate (see reference table showing daily Equation of Time).
The Sandburg Sundial features a correction for longitude (note that the gnomon is offset slightly from the meridian) so that Solar Time will coincide with Standard Time (after adding/subtracting Equation of Time). Add one hour for Daylight Saving Time.