Astronomy Lab Name ______
Observing the Sun
Introduction: In this lab you will observe two layers of the Sun with specialized solar telescopes and hopefully see some magnetic storms and solar eruptions. In addition, we will be doing some simple experiments.
When observing the Sun, special care must be taken to protect the eyes. Blindness may result just by staring at the Sun on any day. Special telescopes have been designed to observe the Sun safely, and we will be using three of them today, in addition to using other safe techniques.
Part 1. Determining the Diameter of the Sun
For this activity, you and a partner will use a solar viewing tube. It looks like this:
1. Measure the length of the tube to the nearest mm: _____
2. Point the black pinhole end of the tube towards the Sun using the “minimum shadow”
technique, which will be demonstrated for you. Do not try to look through the tube.
Look for a tiny circle of sunlight projected on the paper at the other end. Move the tube
until the circle projects on the mm grid, and measure the diameter of the circle in mm:
Measured experimental diameter of the Sun: _____
Using the principle of similar triangles, you can calculate the Sun’s diameter by means of a ratio, if we know the distance from Earth to the Sun, which is 150,000,000 km:
3. Fill in your measurements and solve for the solar diameter:
Sun’s real diameter (km) = experimental diameter
150,000,000 km experimental distance
Sun’s diameter = ______km Show your work:
Part 2. The RBSE Solar Telescope
4. This small telescope is designed to safely view the visible surface of the Sun and any
sunspots. The Sun’s image is projected onto the sheet of paper. What layer of the Sun is
this? ______
5. Notice that the edges of the Sun on the projected image are darker than its center.
What is the reason for this?
6. Why does the solar image appear to move across the paper?
7. Measure the diameter of the Sun in mm. Then, look for sunspots. Find the biggest
sunspot and measure its diameter in mm. Record your numbers below:
Sun diameter ______mm Sunspot diameter _____mm
8. The diameter of the Sun is 1,392,000 km. Set up a ratio to calculate the diameter of
sunspot:
Sunspot’s measured diameter (mm) = sunspot’s real diameter (km)
Sun’s measured diameter (mm) Sun’s real diameter (km)
Diameter of the sunspot: ______km Show your work:
9. The diameter of Earth is 12,756 km. Set up a ratio to calculate the relative size of
the sunspot compared to Earth:
sunspot’s diameter (km) Show your work:
Earth’s diameter (km)
The sunspot is ______times the diameter of Earth.
10. Now quickly trace a curve around the leading edge of the Sun’s image and time exactly
how long it takes to completely leave the circle: ______seconds
11. The apparent diameter of the Sun in our sky is 0.5 degrees. The Earth rotates once each
day, completing a 360o circle. Use this information to calculate the length of a day on Earth:
x seconds = y seconds
0.5 o 360 o
Show your calculation set-up below:
Now change seconds to hours and minutes:
Part 3. The Coronado Personal Solar Telescope
12. This telescope is designed to safely view the lower, red-colored atmosphere of the
Sun and eruptions of hot plasma that are thrown upwards from the surface. What
layer of the Sun is this? ______
14. Some eruptions may be seen to curl back towards the surface of the Sun, making
loops or arcs. What causes them to curve like this?
Part 4. The Schmidt-Cassegrain telescope with solar filter
This telescope shows the surface of the Sun, as seen projected in Part 2, but it is highly magnified so that you can get a better view of the surface and sunspots.
15. In the space below, sketch a sunspot showing and labeling its two zones, the umbra and
penumbra:
16. What does the varying degree of blackness of the spot represent?
If there is still time left, you can play with the giant mirror. It is great for burning things, sometimes even a marshmallow or two!