How to Make a Simple Heilodon

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How to Make a Simple Heilodon
Description 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.
Keywords Solar, sun, movement, earth, heliodon, time, declination, declination angle, altitude angle, altitude, latitude, longitude, solar noon, azimuth angle, sunrise, sunset
Uses Teaching tool to show shadow effects
Authors AAH431
Status Open design
Made? No
Replicated? Was this project made independently by someone other than the authors and without their guidance? No
Published 2015/07/06
Countries of design United States
Category:Dominican Republic
Affiliations Humboldt State University
Materials 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
Sustainable Development Goals SDG04 Quality education
SDG09 Industry innovation and infrastructure
Documentation data
Language English
Manifest data
Language English
Updated 2020-07-12
Author Megan Moore
Author affiliation Appropedia
Author email info@appropedia.org

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')
(0°00')
(+11°39') (+20°04') (+23°26')
July August September October November December
(+20°36') (+12°19')
(+0°57')
(-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.