ASTRONOMY LAB - Safe Gazing at the Sun
WARNING: Never look directly at the sun or at a reflection
of the sun.
DO NOT USE sunglasses, smoked glass, or improper
welder’s glass. Use only the methods listed below.
OBJECTIVES:
Describe sunspots and the sunspot cycle.
Briefly describe or define: flare and prominence.
Find an image of the sun on the web. Go to http://sohowww.nascom.nasa.gov/ and click on
Sunspots in the top right.
View the sun using a number of safe techniques. Describe and sketch these techniques.
View and sketch sunspots.
Keep clear, concise records of what you see and how you did it.
BEFORE YOU COME TO LAB:
Read about sunspots, the sunspot cycle, flares and prominences. (Chapter 8 in The Cosmic
Perspective Fundamentals textbook or on the internet)
Read this write-up.
In your notebook, label the top of a right page with the title “Safe Gazing at the Sun” (Table of
Contents too).
Under the title, write a brief paragraph describing sunspots, including their size, why they look
dark, and the sunspot cycle. Also briefly describe or define flare and prominence.
On the day of the exercise (or one day before), go to: http://sohowww.nascom.nasa.gov/
Click on the “Sunspots” image of the sun (upper right corner) to enlarge it. Print out the image
and tape it in your notebook.
Decide if you want to bring a camera or a cell phone to take pictures of the setups. It is helpful
but not necessary.
BRING TO LAB:
This write-up, a pen, your notebook with the information listed above written in your notebook
and with the solar image taped or stapled in your notebook.
LOCATION and TIME:
Check the calendar and your email for any last minute changes due to the weather.
PROCEDURE:
Form into groups of 2 or 3. Keep your own record.
Record, sketch, or describe: Your location, the date and time, the names of your observing
partner(s), and the weather and sky conditions.
For each viewing technique, sketch and label or clearly describe what you see on the sun.
Also sketch and/or describe the instruments used and how they are set up. Another person must
be able to duplicate your work from your record. You may use the photos from the next few
pages. Cut them out and tape them in your notebook. Make any additional notes about the
equipment and its use. Sketches are fine too. You are welcome to use a camera such as your cell
phone and include those pictures.
Safe Gazing at the Sun Page 2 of 5
WARNING: Never look directly at the sun or at a reflection of the sun.
DO NOT USE sunglasses, smoked glass, or improper welder’s glass.
OBSERVATIONS:
Observe the sun using each of the following techniques in any order. Record the setup and
your observations for each. You may use the pictures in this write-up.
Safe Projected Images of the Sun
The following 1-5 methods PROJECT the sun onto a screen.
1. Safe Projected Image of Sun - Pin hole method– Index cards
Sun at your
back
Pin hole
Use two index cards, one blank and one with a small hole in it.
Stand with your back to the sun. Hold the hole card on your
shoulder. Hold the blank card at arm’s length from the hole
card so that the sun shines through the hole onto the blank card.
Try varying the distance between index cards. What do you
notice? If you hold the card twice as far away, how does the
brightness of the sun’s image change? You probably will not
see sunspots with this method but it is a safe and cheap way to
look at a solar eclipse.
Clean white card
2. Safe Projected Image of Sun - Pin hole method – shoe box
Sun at your
back
Pin hole at this
end toward Sun
The shoe box has a pin hole in the aluminum foil at one end. Hold
that end toward the sun and look at the image inside the box. Again
you will probably not see sunspots with this technique but this
method works well for solar eclipse viewing.
Safe Gazing at the Sun Page 3 of 5
WARNING: Never look directly at the sun or at a reflection of the sun.
DO NOT USE sunglasses, smoked glass, or improper welder’s glass.
3. Safe Projected Image of Sun - Small hand held telescope.
DO NOT LOOK THROUGH A TELESCOPE AT THE SUN unless it is filtered. See 6 -9
below.
Note tape “stopping down”
the sun light
Project the image of the sun unto a piece of paper. Check that the
objective lens (big lens) is partially covered with tape (called
stopping down the lens). If you allow too much light to enter the
telescope, the concentrated energy may ruin the telescope. Adjust
the distance between the telescope and the paper to obtain a crisp
image of the sun (about 1 m). You will probably see sunspots
with this method if you adjust carefully.
Project image of sun onto card
4. Safe Projected Image of Sun - Sunspotter
Put a fresh index card in the inside holder of the Sunspotter.
Adjust the device to obtain a clear image on the index card.
Quickly trace the sun and the sunspots on the card.
Tape/staple the paper in your notebook.
Trace sun and sunspots
on card here.
5. Safe Projected Image of Sun - Reflecting telescope (Red Astroscan telescope).
The telescope projects the sun's image onto a white plate.
Sunspots should be visible. Note the tape over the front
end of this telescope, stopping down the light.
Sun’s image here
Note “stopped down”
opening here
Safe Gazing at the Sun Page 4 of 5
WARNING: Never look directly at the sun or at a reflection of the sun.
DO NOT USE sunglasses, smoked glass, or improper welder’s glass.
Safe Filtered Images of the Sun
The next three methods (6 - 8) safely FILTER the sun’s rays.
6. Safe Filtered Image of Sun - Welder's glass (#14).
Please hold the glass by the edges to avoid smudging.
Observe the sun directly through the glass. You might
see a sunspot if it is big enough.
7. Safe Filtered Image of Sun – Wide band-pass solar filter on 10” Dobsonian telescope.
View the sun directly through the
eyepiece of the telescope with the
solar filter placed over the
telescope. Note the shiny surface
of the filter that cuts out over
99.99% of the light entering the
telescope.
Sunspots should be
visible. Look for any fine structure
of the sunspot as well as bright
areas very near the sunspots. Also
look carefully for granulation
(surface of sun looks like an orange
peel).
Note
solar
filter
8. Safe Filtered Image of Sun - Solar Max Telescope with H-alpha filter (narrow band-pass filter)
Safe Gazing at the Sun Page 5 of 5
WARNING: Never look directly at the sun or at a reflection of the sun.
DO NOT USE sunglasses, smoked glass, or improper welder’s glass.
H-alpha filter
Eyepiece
View the sun directly through the eyepiece of the
telescope. Note the red filter built right into the front end
of the telescope. This telescope filters out all wavelengths
except 656 nm. Look for prominences.