Design an Analemmatic Sundial For Your Latitude

1. Design an Analemmatic 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 Analemmatic 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 Analemmatic Sundial slide. 9. No need to cut out the dial. All you need is a vertical gnomon to cast the shadow. A soda straw or pencil and a bit of clay to hold it work well. Be inventive to find your own gnomon. It’s height does not matter. 10. Place the Sundial in a sunny spot with the 12 o’clock hour of the dial pointed North (South for Southern Hemisphere). Place the gnomon on the center line for today’s date. 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. 12PM 11AM 1PM 10AM 2PM 9AM 3PM jul 8AM 4PM jun aug may 7AM 5PM sep N apr 6AM 6PM W E oct S mar 5AM 7PM Lat = 38 nov feb dec jan Cut Dial Out Along Line Tab Cut Out Gnomon This Edge Toward 12PM Tab North American Sundial Society Draw Dial 38 Clear

3. The Sundial Compared to Mean Time