Project data  

Authors  AAH431 
Status  Open design 
Completed  2015 
Made?  No 
Replicated?  No 
Instance of  Heliodon 
Export to  Open Know How Manifest 
Page data  

Type  Project 
Keywords  altitude, altitude angle, azimuth angle, declination, declination angle, earth, heliodon, latitude, longitude, movement, Solar, sun, time, solar noon, sunrise, sunset, Protractor, calculator, light, Internet access, pencil, thick poster, thick cardboard, house figures, tree figures, wire, wire snipers 
SDGs Sustainable Development Goals  SDG04 Quality education SDG09 Industry innovation and infrastructure 
Authors  AAH431 Megan Moore 
Published  2015 
License  CC BYSA 3.0 
Affiliations  Campus Center for Appropriate Technology (CCAT) Humboldt State University (HSU) 
Language  English (en) 
Translate to  Français, Español, Kiswahili, 中文, العربية, Русский, more 
Export to  PDF, LaTeX, EPUB, ODT 
Page views  158 
Cite as AAH431, Megan Moore (2015). "How to Make a Simple Heilodon". Appropedia. Retrieved 20211022. 
Location data  



Location  Dominican Republic 
A heliodon shows the movement of the sun's movement across the earth for a certain longitude and latitude and a set day for twelve months. Follow the instructions on this site to build one.
A Heilodon is a model of the suns movement across the earth and is a great teaching tool to show shadow effects. There are many different types of heilodons that you can make. Some models can show the suns movement for all latitudes and longitudes and during all das of the year. This page will describe how to make a simple heilodon for a set longitude and latitude and a set day for twelve months.
You will need a protractor, a thick poster or cardboard, wire, wire snipers, a pencil, the radius of your circle, small figures to represent a house/trees, a calculator with invSIN and invCOS functions, a light and Internet access.
To begin you will need to pick a location and find the latitude and longitude of that location.
On your cardboard or poster, make a perfect circle and make north, south, east and west. Also, mark the angles for north and south to use later. Directly north is angle 0 degrees and directly south has an angle of 180 degrees. Solar noon will occur along the line connecting the north to the south.
You will need to calculate the altitude angle for Solar Noon for your location using the latitude of your location and for the 21st of every month you can use the table provided. If you want to use a different day of every month, here is a complete table of declination: http://www.wsanford.com/~wsanford/exo/sundials/DEC_Sun.html
January  February  March  April  May  June 

(20°05')  (10°52')  (+11°39')  (+20°04')  (+23°26')  
July  August  September  October  November  December 
(+20°36')  (+12°19')  (10°29')  (19°47')  (23°26') 
If your latitude is north of the equator you will subtract the declination angle from your latitude angle. If the value is negative that is how many degrees up from the marked north line your altitude will be. If your value is positive, that is how many degrees up from the marked south line your altitude will be.
Equation for 18 degrees north
June 15th
18°  (+23°26') = 5°26' Solar noon will be 5°26' towards the north from perpendicular from the center of your circle.
December 15th
18°  (23°26') = 41°26' Solar noon will be 41°26' towards the south from perpendicular from the center of your circle.
If your latitude is south of the equator you will add the declination angle to your latitude angle. If the value is negative that is how many degrees up from the marked south line your altitude will be. If your value is positive, that is how many degrees up from the marked north line your altitude will be,
Equation for 18 degrees south
June 15th
18° + (+23°26') = 41°26' Solar noon will be 41°26' towards the north from perpendicular from the center of your circle.
December 15th
18° + (23°26') = 5°26' Solar noon will be 5°26' towards the south from perpendicular from the center of your circle.
Using the inverse Sin and inverse Cos functions on your calculator, use the altitude angle that was calculated for each month for inverse sin and inverse cosine. Multiply these new values by the radius of your circle. Inverse Sin will give you Y values for solar noon and Inverse Cos will give your x values for solar noon.
For the azimuth angle for sunrise and sunset you can use this site : http://www.sunearthtools.com/dp/tools/pos_sun.php You can set the location and date and it will provide azimuth angles for sunrise and sunset. These values will be on the same plane as your circle and you do not need to calculate sin and cosine values.
Once all values are found, you can mark them on your circle and use wire to show height and angle for altitude. Once all sunrise, sunset and altitude angles are marked, use small figures. Use a small light to go across each days to see how shadows will form. Remember that the sun rises in the east and sets in the west.