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How to Observe Sun and Solar Eclipses Safely?

Viewing the Sun is more than just an astronomer’s muse - with proper tools, anyone can can witness sunspots across the surface, filaments stretching across the disk, prominences projecting above the chromosphere or even solar eclipses as the Moon passes in front of the face of the Sun.

Unfortunately, viewing the Sun comes with many risks. Looking directly at the Sun with the naked eye should be absolutely avoided - no matter what. It can and will cause permanent, irreversible eye damage. Looking at the Sun through an optical device, such as telescopes and binoculars, only amplifies this effect - taking just milliseconds to permanently damage your eyes. Therefore, learning how to look at the Sun with the proper precautions is vitally important so that we can reduce these risk factors and reap the benefits of sungazing.

Thankfully, there are ways you can observe the Sun and a solar eclipse that are completely safe, easy, and tons of fun!

Harmful Effects of Looking at the Sun

While viewing the Sun can be fun, looking at it directly can damage your eyes within a matter of seconds. Looking through binoculars, a telescope or with your unaided eye allows harmful light to burn the light-sensitive cells causing loss of vision, blind spots and even blindness - making special filters absolutely necessary to observe the Sun.

The Light Spectrum

The light emitted from the Sun occupies a large spectrum. Even when you think you have filtered it out its harmful rays, there may still be invisible bands that carry a lot of energy that will harm your eyes. Interestingly, it’s worth mentioning that the eye doesn't have pain nerves, meaning an individual wouldn't feel any pain or physical discomfort while their eyes are being cooked.

These Sun is bad for your eyes because of the wavelengths of light it emits.

More specifically:

  • The Sun emits light in the infrared spectrum - a wavelength of light that is completely invisible to our eyes, but is extremely harmful, energetic and heat carrying light. This intense energy is used in the medical field for intense heat treatments.. Imagine what it would do to your eyes?!?
  • Even the light emitted by the Sun in the visible spectrum (the type of light we can actually see with our own eyes) is still extremely bright, energetic and harmful.
  • Ultraviolet (UV) light emitted by the Sun is extremely energetic. Although it is outside of the visible spectrum, making it invisible to our eyes, its high intensity has the ability to essentially burn your retina. For example, mountain climbers must wear dark sunglasses, otherwise they get sunburns on their retinas without even looking at sun. Even when layers of sunglasses are used, some bands of the spectrum may pass, injuring the eyes.
Light spectrum

Looking at the disk of the Sun can cause permanent eye damage even when looking at only a thin crescent. In fact, even when just 1 percent of the of the Sun is visible, it is still 10,000 times brighter than the full moon. This is why, to observe the Sun safely, 99% of the Sun’s light must be filtered out before you can view it safely.

Once your retina is destroyed, there is no healing it, no replacing it, and no way to return your vision. Small children are at greatest risk for this because they are inherently unaware of the Sun’s harmful effects.

Can You View a Solar Eclipse with the Naked Eye?

Actually, yes! During the event of a total solar eclipse, there is a momentary period when the Sun is completely covered that you can actually view the Sun with the unaided eye. It is in this moment that astronomers wait years to witness with their own eyes. It is a highly regarded event. Keep in mind, it is only this few minutes, or even seconds, when it is safe to actually look up at the Sun.

But this should be done very, very carefully. During the partial phases of the eclipse, the intensity of the sunlight is still far too strong to safely view the Sun. This remains true even though the Diamond Ring Effect. ONLY at absolute totality should you take advantage of viewing the eclipse directly.

To observe sun safely, we need to effectively block out all bands of harmful light...

We cannot over emphasize this: You need to protect your eyes when observing sun or solar eclipses.

What Not to Do?

As previously mentioned, even when the Sun appears to be safe to look at i.e. with dimming sunglasses, for example, the invisible wavelengths of light make viewing the Sun extremely dangerous. Therefore, even if you think looking at the Sun seems safe and even though you may not feel any physical pain when doing it - looking at the sun without proper equipment should NEVER be done.

Another unsafe viewing method is stacking multiple pairs of sunglasses on top of each other and then looking at the Sun. Although the sunglasses appear to dim out much of the visible light, the high energy wavelengths (which cause the most damage) are not only still penetrating the glasses, but you actually make your eyes more susceptible to accepting this high energy radiation - causing even more severe damage.

Additionally, do NOT look at the sun using soot covered glass, CDs or DVDs. Again, although the light appears dimmed, the glass does not effectively block harmful, invisible light from entering your eyes.

Safely Observing an Eclipse

There are many different options for viewing the Sun directly during a solar eclipse.

Eclipse Glasses

One of these can be as simple as purchasing an inexpensive pair of solar sunglasses from companies such as Rainbow Symphony, which can be readily found online. Remember, before directly viewing the Sun to test your solar shades by putting them on and looking around. If they are in viewing condition, you should only be able to see darkness as solar shades reduce the lighting by 99 percent. If you see any light, your sunglasses have a crack or some other defect, making them unsafe to look at the Sun.

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Welders' Goggles

Alternatively, you can purchase dark glass that welder’s use to protect their eyes. The glass plate is called #14 arcwelder’s glass which you can get from your local hardware store. A good protective lens will not just block visible light, but they will also block over 99% of UV light and IR radiation.

These glasses block out enough of the harmful light, both visible and invisible, to allow for direct viewing of the Sun. However, they DO NOT provide protection if placed behind a pair of binoculars or telescope. Since these devices magnify and concentrate the power of the Sun, the glass will actually crack and break after being exposed for just a few minutes. When using an optical viewing device, only use a specially designed solar filter on the front end (where the Sun comes in) of the instrument.

Although this method is easily retrievable, they do make the Sun appear to be an unnatural green color, somewhat taking away from the seemingly direct view of the Sun. Also, keep in mind that other filters such as smoked glass, polarized filters, stacked sunglasses, etc. are not sufficient protection from the harmful light from the Sun.

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Pinhole Camera

A perfectly safe and easy way to view the Sun during an eclipse (or any other time) is by using a “Pinhole Camera”. You may have used this method to look at the Sun as an experiment when you were growing up. The method allows you to indirectly view the Sun’s projection onto an alternative screen. Don’t be fooled though, this method is precise, easy to create, and allows you to witness the entirety of an eclipse and even see sunspots!

Pinholes perfectly focus any object at any distance without the need of any other optical elements such as lenses etc. When projecting the Sun, a bright beam of perfeclty focused sunlight will be projected onto a piece of paper. To create this effect, all you must do is poke a small, clean hole into a piece of cardboard or paper such as an index card. Face this piece of paper toward the Sun. Place another piece of paper behind the shadow of the first, creating a type of screen. The hole will project a small inverted image of the Sun onto the second card displaying a perfectly projected image onto the paper.

What Will You See?

During a solar eclipse, you can clearly see the eclipsing phases of the Sun as the Moon passes in front of the disc. You can repeat this with different sizes of holes in the first piece of paper to find the size that will create the clearest image. A larger hole will be a brighter image, but less clear. A smaller hole will be a bit more dim, but will be sharper. Additionally, if you’d like to make the image larger, move the second sheet of paper, the screen, farther from the pinhole. To make it brighter, move it closer.

If you ‘d like the clearest image possible, place the hold onto a viewing card enclosed in a long box - the longer the box, the larger the projected image. To do this, you will need: A long cardboard box, a sheet of white paper, some aluminium foil, scissors, and tape.

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Do It Yourself

The setup is shown below:

Pinhole observation box

Of course, this diagram can be modified to your personal preferences. For example, one side of the box (preferably the bottom) could be completely removed so that your head could move easily in and out of the box. Keep in mind that this will reduce the apparent darkness inside the box, reducing the contrast of the image.

Remember, do not look through the pinhole at the Sun.

A Better Pinhole Projection Method

To amplify the elongated box method, you can actually create an even more effective way of looking at the Sun by using a room with a window, depending on the time of day, of course. Find a room with a window that is facing the same direction as the Sun. Turn off all the lights and close any shades, making the room as dark as possible.

Next, create the same kind of pinhole setup as previously described by punching a hole in a card and placing it near the top of the window. Place the second piece of white paper, acting as the screen on the other side of the room to display the Sun’s image. You could even use just the surface of your wall if it is white and smooth. As before, you can vary the size of the hole to try and create the clearest image possible.

Telescope Projection Method

Observing the Sun using a telescope or binoculars offers a clearer, more direct view of the Sun during an eclipse. It is important to keep in mind that these optical instruments also focus and concentrate sunlight, making it especially important to make sure you are using the appropriate filters safely.

By using a telescope (or even binoculars), you can use the same type of method to project an image of the Sun onto a screen.

The set up is shown below:

Telescope projection method

The cardboard shield prevents additional, unwanted light from falling on the screen.

Although using a telescope is a great way to view the Sun, it does take in a lot of sunlight, which can quickly overheat the internal components. Because of this, only smaller telescopes should be used, such as telescopes with an aperture less than 4 inches. If you have a larger telescope, you can adjust for this by placing a cover over the front end and cutting a smaller, 3 to 4 inch hole to take in sunlight.

Remember, when using a telescope to view the Sun to cover or remove your telescope’s finder so that it is not damaged by the sunlight.

Additionally, it should be mentioned that this method should only be used in a controlled setting. If there are children present, make sure that the telescope is not directed towards the Sun and left unattended. If a child were to peer through the scope while pointed at the Sun, it will almost immediately blind them.

White Light Filter

Although there are a few different ways you can use a telescope or binoculars to view the Sun, a white light filter over the front end of your aperture is a simple solution that allows you to view the Sun directly.

A white light filter effectively filters out 99 percent of the light transmitted by the Sun, making the image you see perfectly safe to look directly at. With this filter, you can see sunspots, and of course, the entirety of the eclipse with more contrast than the pinhole camera method.

These filters can be easily bought for just $20 - $30, although you can make them yourself using appropriate solar film. This type of white light filter allows you to view the Sun’s surface, the photosphere, making the Sun appear a pale yellow or orange color. Sometimes, it can even be blue, depending on the type of filter you purchase. Additionally, you can see sunspots along with other interesting features, depending on how active the Sun is. During an eclipse, directly viewing the Sun while the Moon passes in front is a completely unique event.

Few things to keep on mind:

  • This type of filters are meant to be used in the front of the telescope. Never, ever, under any circumstances use them at the back of your telescope. Solar light will be too strong, first burning a hole in the filter, then in your retina, in a matter of split seconds.
  • Make sure that the filter is mounted securely either via built in screws or a strong, high quality tape that won't give way in the heat of sun. If it can be knocked off, it will leave your telescope unprotected, and your eyes at risk of getting injured.
  • Remember to keep your telescope pointing away from the Sun before and after using your filter.
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Hydrogen Alpha Solar Filters

More specifically, by allowing hydrogen-alpha at 656.3 nanometers or the calcium-K line at 393.3 nanometers, you can suddenly see features such as prominences, filaments, and if you're lucky, maybe even a solar flare! With this view, you could witness a solar eclipse with maximum potential. Unfortunately, these advanced filters can be quite costly.

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Varying greatly in price, these will give progressively better image as you go up in performance. That said, even the cheapest version gives an image that is absolutely unequelled by any other method mentioned above.

Recommendations for Each Phase of the Eclipse

Each phase of the eclipse presents different viewing opportunities. If you’ve managed to gather multiple viewing options or have decided to an attend an event with different viewing opportunities, there are different times that offer different views.

Before the eclipse starts, hydrogen alpha telescopes allow you to view all kinds of features, such as high activity regions, sunspots, filaments, or prominences. These are always interesting viewing opportunities when it comes to viewing the Sun. If you do not have a hydrogen alpha telescope, you can always use the reflection methods, previously described, to view sunspots as well.

During the partial eclipse, eclipse glasses along with the reflection method allow you to clearly view the Moon beginning to pass in front of the disk of the Sun.

During totality, your best optical instrument is your naked eye! Since this phase lasts the shortest period of time and is actually the only moment when looking directly at the Sun is safe, it’s worth putting down the optical instruments and taking in the scenery, naturally.

Solar corona
Live from NASA! LASCO (Large Angle Spectrometric Coronagraph) is able to take images of the solar corona by blocking the light coming directly from the Sun with an occulter disk, creating an artificial eclipse within the instrument itself. The position of the solar disk is indicated in the images by the white circle. The most prominent feature of the corona are usually the coronal streamers. Occasionally, a coronal mass ejection can be seen being expelled away from the Sun and crossing the fields of view of both coronagraphs. The shadow crossing from the lower left corner to the center of the image is the support for the occulter disk. This image show the inner solar corona up to 8.4 million kilometers (5.25 million miles) away from the Sun. -Courtesy of NASA

Additionally, you can use binoculars if you insist on seeing the corona up close. But be careful, when you are about to see Baily's beads, it is over and time to stop viewing immediately.