Measuring the elevation angle of the sun.

After much frustration, using wobbly paper and uneven surfaces, pens that don't work and and old plastic protractor, I found that the safest and most accurate way of measuring the elevation angle of the sun is the dioptra.

A long tube..
Plastic
Cardboard
Anything!

Just so long as it is fairly long, light enough to hold with one hand and you can fix a protractor to it.




Method of use.
  1. Stand with your back to the sun
  2. Hold the tube with one hand
  3. Hold your other hand close to the lower end of the tube so that the sun disc will be projected onto your palm when the tube is tipped upwards at the same angle as the sun.
  4. Tilt the tube so that a bright disc of light is projected onto your palm.
  5. Or onto the ground.
  6. Read the angle from the protractor.


'Clear disk' on the ground shows that the tube is pointed directly at the sun.


Why this is a good method!
Shadows are excellent, but...the post must be vertical, not leaning to one side. The ground should be perfectly level or else the shadow will be distorted. I was surprised to find that I did not need to have a perfectly vertical screen for the disc of light to be projected upon. It is possible that a longer tube length increases the accuracy.



Finally...
For dunces at maths. The elevation angle of the sun in this picture is....23 degrees. I had to think long and hard about that. I am a dunce at maths.

Comments