If you want to look at the solar eclipse, sunspots, or just the Sun in general, you should NOT look at it directly!
You can look at the Sun safely using indirect methods, like pinhole or binocular projection, or using solar filters or solar telescopes. These might sound a little daunting, but you can build them from scratch all by yourself.
Read on to find out why it’s worth having a go.
Let’s start off with the simplest and safest one. A pinhole projector, as the name suggests, has a small hole through which sunlight passes.
The Sun’s image is then projected onto another surface opposite the pinhole opening. You observe the solar image on that surface.
WARNING: Pinhole projector does not mean that you look at the Sun through a pinhole.
How to Set up a pinhole projector
- 2 stiff sheets of paper or card
- A sharp pin or a needle
What to do:
- Take one sheet of your paper or card and make a tiny, round, smooth hole using the needle or the pin.
- Face your back to the Sun and hold your pierced paper above your shoulder so that the Sun shines onto it (please don’t be tempted to look at the Sun directly!).
- Hold the second sheet of paper behind the first so that sunlight coming through the pinhole is projected onto it. This second sheet of paper (or card) acts as a screen.
- Because the Sun’s rays (which travel in a straight line) intersect at the hole, as shown by the red lines in the diagram above, the resulting image is inverted.
- Increase the distance between the sheets of paper to make the image bigger, and decrease the distance to make it smaller.
What Can You See?
You can use this method to view solar eclipses where the ‘bite’ taken out of the Sun by the Moon is large and dramatic.
However, because the hole in your pinhole projector is tiny, the resulting image has a soft-focus, caused by diffraction. This means that details like sunspots, which need a sharp level of focus to be revealed, cannot be viewed.
Telescope or Binocular Projection
It works similar to the pinhole projector, only with a much wider lens. This bigger aperture allows much more light to come in, thus more detail to be seen.
How to Set up a Telescope or Binocular Projector
- A small telescope. Larger telescopes are easy to overheat when the Sun is pouring light down their tube, so limit this to binoculars or telescopes with an opening no wider than 5 cm or 2 inches.
- You can use a larger scope if you limit the sunlight falling into it. If your telescope has an aperture wider than 5 cm, cut a 5 cm circular hole in a sheet of card and attach it to your telescope’s aperture (the wide end facing the Sun). For binoculars, cover one objective lens completely.
- A white sheet of stiff paper or card to project the Sun’s image onto.
What to do:
- Place either your telescope or binoculars on a tripod or a steady surface.
- Point the objective lens towards the Sun and place a white stiff sheet on the back end for the projected image to appear.
- The sunlight enters through the objective and can be focused by your telescope/binoculars and projected onto the white paper.
What Can You See?
You can use this method to view sunspots. However, remember to keep moving the binoculars and telescope away every few minutes so that the devices don’t overheat because of the focused sunlight.
The video below from ‘More than the Sum’ shows you exactly how to do this with your telescope.
Solar filters are filters attached to your viewing instrument so that your eyes don’t take the full force of the Sun’s rays and allow for safe viewing.
The Sun is so bright, and telescopes magnify light so much, that these filters block out 99.9% of the incoming sunlight to protect you. This means that they let through just one in every thousand photons… and we can still observe the Sun through them.
Solar filters (Amazon link) are made up of metal-coated glass, mylar, or plastic. Both metal-coated glass and mylar offer clearer views and better quality than plastic. They are also more durable.
These filters are best placed securely in front of your telescope’s primary aperture (main opening) to block out the majority of the sunlight before it enters your instrument.
This is especially important for large, sensitive equipment because it keeps the heat out as well as the light. Pointing your telescope unfiltered at the Sun will cause heat to build up, making glass, metal, and plastic expand and crack.
What Can You See With a Solar Filter?
Solar filters are the best option for observing the Sun with your existing telescope. With the magnification it provides, you’ll see the surface of the Sun, its texture, sunspots, and granulation detail.
A mylar filter results in a blue Sun, offering better contrast between the Sun’s disc and the bright spots on the Sun’s surface called faculae.
A glass filter produces a yellow-to-orange Sun because the filter itself is coated with Nickel or Chromium.
Another type of filter, called the Hydrogen-Alpha, only lets through certain wavelengths of light. This shows you the texture of the Sun’s surface.
Because the Sun is so large, bright, and close, you don’t need a humongous telescope to observe it in detail. A refractor with a 3-inch diameter will suffice, so solar astronomy is open to all of us with even a modest telescope who can invest in a solar filter for it.
If you want to look at the Sun in detail over time, i.e. it’s more than a passing interest, then a solar telescope is the ultimate choice for solar astronomy.
Solar telescopes are specifically designed to sustain the incoming heat from the Sun while maintaining a high resolution for detailed images. They are built to make them safe for viewing the Sun all day long.
Their aperture sizes range up to around 4 inches, which doesn’t sound like much, but the best dedicated models become incredibly expensive at this size. They are meticulously constructed for their purpose, i.e. they should cope with staring at the Sun for many years, and can be refined to just reveal certain wavelengths of light.
Because they produce highly detailed images, they need low turbulence and low water vapor content in the air to minimize light scattering.
This is why you’ll find that these solar telescopes are placed at high altitudes on the mountains, where the air is thin and reliably dry.
Although these telescopes are made for safe solar viewing, don’t gaze directly at the Sun through the eyepiece. Remember to use a right-angled eyepiece so that you are gazing down into your scope when it is pointed at the Sun. This will prevent you from being sun-dazzled (or blinded) when you accidentally open the eye not looking in the eyepiece.
What Can You See With a Solar Telescope?
You can see all of the Sun’s features in great detail since solar telescopes are usually used for research purposes and thus produce high-resolution images.
Orion’s personal solar telescopes’ price ranges from $699 to $1,199. Solar telescopes not only transmit a fraction of the sunlight, but they also narrow down that sunlight into specific wavelengths.
While deciding whether or not to buy a solar telescope, think of how it’ll be used — it is a good choice if you want all of these specifics, otherwise a simple telescope would do. You might also decide that it is enough to have a high-quality solar filter for your existing telescope.
There are various methods to look at the Sun safely: pinhole projection, personal telescopes and binoculars fitted with solar filters, and solar telescopes.
You can build a pinhole projector, add a filter to a telescope to make it safer to view through, or use solar filters, or select from a range of solar telescopes built exclusively to observe the Sun safely.
Filters work by blocking out the majority of the sunlight so that the final image is focused, detailed, and less harmful. Solar telescopes are the ultimate instrument for solar astronomy, with their rugged reliability and precision build.
The amount of detail seen in the final image depends on the specifics of the instrument, but all of them provide equally satisfying experiences of viewing the Sun.
Written by Sharmila Kunthuner