You will need
  • - the gnomon;
  • - the range;
  • - horizontal surface;
  • - liquid level to establish a horizontal surface;
  • calculator;
  • table of tangents and cotangent.
Find a strictly horizontal surface. Check it with a level. Can be used as a bubble and an electronic device. If you use liquid level, the bubble should be exactly in the center. For the convenience of further work attach on the surface of a sheet of paper. It is best in this case to use the graph paper. As a horizontal surface it is possible to take a sheet of thick durable plywood. It should be free of depressions and mounds.
On graph paper draw a dot or a cross. Install the gnomon vertically so that its axis coincides with your mark..the Gnomon is called a vertically mounted rod or pole. Its top has the shape of a sharp cone.
The gnomon is a vertical rod
At the end of the shadow set the second point. Mark it as point a, and the first — point C. the height of the gnomon you must be known with sufficient accuracy. The larger the gnomon, the more accurate will the result.
Measure the distance from point A to point C in any way you can. Please note that the unit of measurement was the same as the height of the gnomon. If necessary, put in the most convenient units.
On a separate sheet of paper make a drawing using the received data. The drawing should be a right triangle, whose right angle With the installation location of the gnomon, side, SA — length of the shadow, and SV side — the height of the gnomon.
Calculate angle a by using the tangent or cotangent using the formula tgА=VS/AC. Knowing the tangent, determine the actual angle.
The resulting angle is the angle between the horizontal surface and the solar beam. The angle of incidence is the angle between the perpendicular to the surface, and beam. That is, it is equal to 90º - A.