Pencil-case DIY solar inclinometer

All you need is a protractor with hole drilled, string, straw, scissors, bluTack. That's it !

>> Follow the instructions below or just watch the video to see how its done  <<

This is an awesome activity to do around the Equinox (mid-late September and March),  Solstice (mid-late December and June), also Matariki !

Participate in the Sun Survey and be in to Win!

How does it work? -

  • Gravity pulls the weight at the end of the string straight down towards the center of the earth, creating the vertical plumb-line.
  • When you carefully tilt the protractor the string stays aligned vertically (make sure it is not dragged by the protractor or swinging).
  • The difference between the vertical and the tilt gives you the angle eg. 90 -75 = 15 degrees
  • Go outside (helps to work in pairs) and measure angles!

Activity 1 - How to measure the sun angle -

Measuring the sun angle in 'pointing' mode

  • Find a wall exposed to the sun.
  • Hold the protractor etc to cast a shadow on the wall - focus on the shadow of the straw.
  • Make sure the protractor is vertical and not affecting the string at all.
  • Orient the "angle-measurer" (correctly called an inclinometer) so that the straw shadow becomes as small as possible and the rays of sunlight shines straight through to form a small circle.
  • Find the angle of the sun by subtracting your reading from 90 degrees.
  • Do this at different times through the day (can be a few days apart) and make a graph to show the sun's path through the sky.
  • Record the sun angle, the time of day and the season.

For another simple Schoolgen STEM activity that achieves the same thing in a different way see - Sun, Shadows and Triangles

Activity 2 - How to measure a roof angle -

Measuring the roof angle in 'side' mode

  • When the straw (viewed side-on) is exactly horizontal the string will 'read' 90 degrees. 
  • Find a suitable roof to measure - you will need to be viewing it in profile so that the bottom of the slope and the top of the slope are about the same distance from you (ridges that slope away will not give accurate readings).
  • Tilt the straw, holding the protractor upright, to visually line up with the roof line.
  • When you carefully tilt the protractor the string stays aligned vertically (make sure it is not dragged by the protractor or swinging) - the difference between the vertical and the tilt gives you the angle eg. 90 -75 = 15 degrees.
  • What roofs would be best for solar panels ? 
  • PRO HINT - Look for roofs with an angle somewhere between 10 and 50 degrees (in NZ 30 degrees is ideal). The roof should face somewhere between north-east and north-west (True North, not Magnetic North).  

NZ Curriculum Links for Teachers

Science (Level 2 - 6):

  • Planet Earth & beyond.
  • Physical World.

Mathematics (Level 3 -4):

  • Geometry & Measurement.
  • Statistics.
  • Number & Algebra.