### Try This! - Print a Sunchart.

Go to the **University of Oregon Solar Radiation Monitoring Laboratory** web page and generate a PDF SunCharts for two locations: (1) State College, PA, and (2) your own location.

1. Download the PDF chart for the orthographic (Cartesian) projection

2. Download the PDF chart for the polar projection

3. Reflect on the charts:

- Can you find key solar days on the chart (equinoxes, solstices)?
- Can you identify sunrise and sunset solar times for different months?
- How does the position of sunrise and sunset vary throughout the year?
- How are these charts different between your location and State College, PA?

Now, based on your understanding of the SunCharts, work through the self-check questions below. While you work through these steps, try to think about all the calculations that went into each plotted point on the curves. You should reflect on the fact that the SunChart tool is simply plotting points and lines based on solar calculations of time and longitude. The same calculations that you are mastering now in class. Pretty exciting!

#### Self-Check Questions - based on the Cartesian SunChart for State College, PA

Answer the same questions for your own locale. Are the answers different or the same compared to State College, PA?

If you check out the polar projection of the Sun Chart, you will see that it looks quite different, but the plot is based on virtually the same data. Here is the polar chart for State College, PA, location. Note that in this case the coordinates used are solar azimuth and solar zenith angle (SZA) as opposed to the solar elevation angle in the cartesian projection (I wish there were an option to switch between those two). If you need to get the solar elevation angles from this plot, just remember that those angles are complementary:

$${\alpha}_{s}=1-{\theta}_{z}$$

#### Polar Sun Chart for State College, PA

This is the projection you will be using for shading analysis in your homework. So take some time studying this plot.

- What is each blue curve represents here?
- Pick a point on a curve. Can you determine the solar azimuth and solar zenith angle for this point from the plot? What would be solar elevation angle at that point?
- Which point on the plot would correspond to 3 pm on February 21st (tip: look for month and hour labels)

Going forward, you can always check your solar coordinate calculations versus the Sun Chart or use them for quick estimates of the Sun position.