Design an Analemmatic Sundial For Your Latitude by psq21886

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									                                     Design an Analemmatic Sundial
                                           For 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.
                                                       12PM
                                  11AM                                     1PM
                         10AM                                                                  2PM


             9AM                                                                                             3PM



       8AM                                                    jul                                                       4PM
                                                 jun
                                                             aug
                                                 may
 7AM                                                                                                                          5PM
                                                              sep
                                                                                              N
                                                 apr
6AM                                                                                    W              E                        6PM
                                                              oct
                                                                                              S
                                                 mar
 5AM                                                                                       Lat = 38                           7PM
                                                              nov
                                                 feb

                                                              dec
                                                 jan


                                   North American Sundial Society

                                                                                                  Cut Dial Out Along Line
             Draw Dial
       38
                                                       Tab




               Clear            Cut Out Gnomon                 This Edge Toward 12PM
                                                       Tab
                           The Sundial Compared to Mean Time


                                      Equation of Time

                          20

                          15
Add or Subtract Minutes
 To Get Standard TIme




                          10

                           5

                           0

                           -5

                          -10

                          -15

                          -20
                                0   100         200          300   400
                                           Day of the Year

								
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