2.14 Try This! Print a Sun Chart

Try This!

Print a Sunchart: Go to the University of Oregon Solar Radiation Monitoring Laboratory [1]web page and download a pdf sunchart for (1) State College, PA, and (2) for where you live.

First, download the PDF chart for the orthographic (Cartesian) projection
Second, download the PDF chart for the polar projection: alternate page for polar projections [2].
Reflect, on the charts:
1. Can you find key solar days on the chart (equinoxes, solstices)?
2. Can you identify sunrise and sunset solar times for different months?
3. How does the position of sunrise and sunset vary throughout the year?
4. How are these different between your location and State College, PA?
Finally, analyze the charts for the self-check questions below.

While you work through these steps, try to think about all the calculations that went into each plotted point for the print out. You should reflect on the fact that the Sun Chart tool is simply plotting points and lines based on solar calculations of time and longitude. The same tools that you are learning about now, class. Pretty exciting!

Self-check questions:

Based on the chart that you've printed, check the answers among your peers in the comments section below for the following questions:

1. Quick reporting: Who has the highest solar altitude in June?

Click for answer.

ANSWER: Post your thoughts in the Lesson 2 Discussion Forum.

2. Quick reporting: Who has the lowest noontime solar altitude in December?

Click for answer.

ANSWER: Post your thoughts in the Lesson 2 Discussion Forum.

3. Why are the arcs "flipped" when comparing your orthographic plot to your polar plot?

Click for answer.

ANSWER: The plots are flipped with the summer arc at the top in the orthographic plot and the summer at the "bottom" in the polar plot. This is because the observer in each plot is oriented 90° from the other: the orthographic plot assumes a vertical standing observer on the ground, while the polar plot assumes the observer is like an eagle flying above the sky dome.

4. Are the arcs representing the hours of the day the same thing as the hour angles?

Click for answer.

ANSWER: Nope. The arcs representing the hours of the day (in solar time) are representative of the distorted hour angle as it is transformed (they have a parametric relation, but hour angles themselves are not represented in the angles of altitude and azimuth for these plots).