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Making a horizontal sundial

To make a horizontal sundial you need a gnomon (a pointer with an angle equal to your latitude) and a horizontal scale. You will also need a compass to set your gnomon and scale so that it lines up with the north- south line where you are.

The horizontal, scale should look like the one drawn below. The lines show the hours. This one is correct for a person at 51o N, you will have to use the table below to draw your own if you live at another latitude.

The table below shows the angle A for different hours at various latitudes

Hours from noon 50o
51o 52o 53o 54o
0 0.0 0.0 0.0 0.0 0.0o
Mercury 4840 58 0.5 87
The angle from the noon line (12:00) is called the hour angle (H). Since the Sun moves through 15o each hour the hour angle is 15 x the number of hours from noon.

You can calculate the angle (A) from the noon line for various hours using your latitude (L).

Don't forget to change the angle of your gnomon to that of your latitude. (/p>

© Keith Gibbs 2020