Design an Octagonal Sundial For Your Latitude

1. Design an Octagonal SundialFor Your Latitude North American Sundial Society Created by: R.L. Kellogg rkellogg@comcast.net Sept 2003 This is an unusual power point presentation. By enabling the Visual Basic macros, you can create your own Octagonal Sundial. The Visual Basic macros have been locked to prevent tampering. If you choose to use this presentation: First, check your power point security setting: Click on “Tools” , “Macro”, “Security…”. Set the security level to “medium”. Exit the Visual Basic code and Power Point program, restart the power point and respond to the dialog box “enable macros”. This will be the normal startup to activate the program features. You are prevented from seeing the Visual Basic code, but if you would like a copy, please email Robert Kellogg at the above email address. 1. Start power point (in “medium” security mode) and “enable macros” 2. On the next viewgraph, the sundial construction slide, enter your school name in the text box. Do not delete this box nor move it “in front” or “in back” of any other object. If you do not care for a name on your sundial, move the text box to the bottom of the slide. 3. At the top of power point, select “slide show” and “view show”. 4. Go to the next slide for dial construction. Click the up and down arrows to select your latitude (+ for north, - for south). 5. Click the “Draw Dial” button. Power Point will draw your Sundial. 6. You may select other latitudes and “Draw Dial” again and again. It clears the display before drawing. 7. You may clear the dial and gnomon by selecting “Clear” 8. End the slide show and print out the Octagonal Sundial slide. 9. Cut out the Sundial plate. Cut out the gnomon and fold it in half. Bend back the gnomon tabs for gluing to the plate. 10. Glue the gnomon to the Sundial plate. High end of the gnomon goes toward 12 o’clock (XII). The gnomon lower point is on a line between 6 am (VI) and 6 pm (VI). 11. Place the Sundial in a sunny spot with 12 o’clock (XII) pointed toward North (South for Southern Hemisphere). Read the time. This is “local solar time” and may differ from your clock “standard time”. You can use the Equation of Time graph to correct the sundial to standard time. Variability in the earth’s orbit around the sun, the earth’s axis tilt, and the sundial location away from the longitude of the time zone may cause the Sundial to be up to 45 minutes off.

2. <-- XII Gnomon Tab N <-- XII Gnomon Tab W E S Lat = 38 North American Sundial Society Draw Dial 38 Clear

3. The Sundial Compared to Mean Time