Make a pinhole viewer to safely observe the Sun
What's this Science Bite about?
You can make an effective pinhole viewer to safely observe the Sun, sunspots or a solar eclipse. During a solar eclipse the Moon’ shadow (‘umbra’) crosses the surface of the Earth. The next total solar eclipse, when the Moon passes in front of the Sun from our viewpoint here on Earth, is on 20th March 2015 and is partially visible from Scotland. For observers in Glasgow, partial eclipse will begin around 08.30am, with the maximum point of the eclipse occurring at 09:34am. The Moon will leave the Sun’s edge and the partial eclipse will be over at around 10.43am.
IMPORTANT: Never look directly at the Sun - even when it is eclipsed. Doing so can cause permanent blindness. UV (Ultraviolet) radiation from sunlight can burn the retinas in your eyes without you realising.
What you'll need
- A long cardboard box or tube about 1.8 metres (6 feet) long. If you don't have a long box, you can tape two or more together to make one long box
- Duct tape
- Aluminium foil
- A sharp pin
- Sheet of white paper (or white card)
- Some sunshine!
How to do the experiment
Follow the instructions in the video below.
Can't see the video above? Watch it on Youtube.
Ask an adult to help. If needed, join several cardboard boxes together with duct tape so that you have one long box which is hollow. Ideally the box for your pinhole viewer should be about 1.8 metres (6 feet) long in order to get a clear, focused image of the Sun.
Using scissors (or a sharp knife), carefully cut a rectangular hole in one end of the long box.
Use the scissors to cut a rectangular piece of aluminium foil that is slightly larger than the hole you’ve cut in the box. Ensure you keep it as flat and smooth as possible.
Use duct tape to attach the aluminium foil to the box, completely covering the rectangular hole you made before.
Carefully make a small hole in the middle of the aluminium foil using a sharp pin.
Cut a viewing hole in the side of the box towards the opposite end from the pinhole. Attach the sheet of white paper (or white card) to the inside of the box to act as a screen where your projection of the Sun and Moon will appear.
With your back towards the Sun, place the box with the hole towards the Sun. Adjust your position without looking at the Sun directly or through the pinhole until you see the Sun's image on the paper through the viewing hole. An inverted image of the Sun will appear. The longer the distance between the pinhole and the screen, the larger the image will appear.
As the Moon moves in front of the Sun during an eclipse, you should see the shadow edge across the image on the paper screen. Remember: do not look at the Sun directly, or through the pinhole.
Find out more...
To observe a total solar eclipse you have to be in the right place at the right time. Total solar eclipses, when the Moon covers the entire disc of the Sun for an observer on Earth are rare as. Several natural phenomena must happen at the same time.
- There must be a New Moon.
- The Moon is near a lunar node – where the orbital plane of the Earth (the ecliptic) and the orbital plane of the Moon meet.
- The Earth, Moon and Sun are aligned in a straight line for a viewer on Earth.
- The Moon is at perigee – the Moon’s orbit of Earth is elliptical. When at perigee, the Moon is at its closest point to Earth on its orbit (‘Apogee’ is the term given to its farthest point from Earth).
Total solar eclipses are possible because the Sun’s distance from Earth is approximately 400 times that of the distance between the Earth and the Moon. By chance, the Sun’s diameter is also about 400 times that of the Moon’s. They appear approximately the same size.
On 20th March 2015, observers in Scotland will be (weather permitting) close to all those conditions being met and see around 80% to 90% of the Sun covered by the Moon.
Partial eclipses and annual eclipses are more common. Partial eclipses are observed when only the lunar penumbra touches the Earth. Annular eclipses occur when the Moon appears smaller than the Sun as it passes centrally across the solar disk. A fourth type is known as a ‘hybrid’ eclipse. When this occurs some viewers observe a total eclipse whilst others observe an annual eclipse.
What happens if you make the pinhole bigger or smaller?
What would happen if you made lots of pinholes?
Could you add photographic paper to capture the image?
Modify your sun viewer – can you make a stand for it?
Planet Earth > Space
SCN 1-06a By safely observing and recording the sun and moon at various times, I can describe their patterns of movement and changes over time. I can relate these to the length of a day, a month and a year.
SCN 2-06a By observing and researching features of our solar system, I can use simple models to communicate my understanding of size, scale, time and relative motion within it.