Solar Mapping II

Now that you have your handy dandy solar chart, you get to have fun with school supplies.

What you need:
A compass (can even be the inexpensive plastic camping ones)
A protractor (Yes, those fun little geometry tools you haven't used since high school)
String
Weight (the ones used for fishing work)
Permanent marker
A friend

Using your compass:
The compass will be used to calculate the azimuth angle for each object you want to plot on your graph (the tree in the front yard, the high rise apartments next door, etc.). In my case, I'll be standing at one of the two potential house sites (I'll be making a separate graph for each possible site). Once there, I will look around me to see what objects might affect sun exposure on the site. There will be a lot of graphing, let me tell you.

What you will do is stand at your site and point your compass to the object you want to graph. Set the degree dial so that the magnetic pointer is on the north/south axis (180 degrees at south end). Now, you need to know how many degrees true north/south is from magnetic north/south for your area. This website will help you figure that out. Be sure to adjust your readings accordingly. The azimuth angle will be the number of degrees east or west of south the compass is pointing. If you are like me, that sounded like jibberish. So, let me give you an example. If your compass reads 150 degrees, the azimuth angle is 30 degrees east of south because there is a 30 degree difference between 180 and 150. Make sense? If the compass number is above 180, it is however many degrees west of south.

Using your protractor:
Craft time! Attach the weight to one end of the string. The string doesn't have to be very long, just longer than the protractor. Attach the other end to the hole in the protractor. Congratulations! You just made your very own sextant. You will use your sextant to calculate the altitude of each object you want to graph. Hold the protractor semicircle down (or flat end up), so that you are able to look across the 0 to 180 line. Look across that line to the highest point of the object you are wanting to graph. This is when you need your friend. Have the friend read the angle measurement where the string rests against the protractor. In other words, if I am holding up the protractor, the weight will be pulling the string straight down. As I angle the protractor to look at the highest point of my object, that string will still be pointing straight down and will rest against the side of the protractor. Whatever measurement it is resting on will be the measurement you note.

You now have the azimuth and altitude angles for each object on your horizon. You can plot them on your graph to see how sun exposure might be affected on that site. Keep in mind that deciduous trees will lose their leaves in winter.

Happy graphing!