Updated Advice for Safely Viewing the Solar Eclipse this Summer

Advice for Safely Viewing the Solar Eclipse this Summer

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May 29, 2019

The solar eclipse of July 2, 2019, draws near, and because there is an increasing number of potentially unsafe eclipse viewers available on the market, we’re updating the safety advice for viewing the solar eclipse this year.

Buenos Aires, Argentina

Before, all you needed to make sure your glasses or handheld viewers for solar eclipse are safe is to look for the logo of ISO (International Organization for Standardization). However, simply stating that the product meets the international safety standard ISO 12312-2 for filters used in solar eclipse viewers is no longer enough to ensure the product’s safety. Why? Because several companies create fake solar eclipse glasses and viewers and print the ISO logo and ISO certification label on those devices. However, those glasses are made with cheap materials that are unsafe for people, since they do not block enough infrared, ultraviolet, and visible radiation of the Sun. Those companies do not take into account people’s health and often support their fake claims with bogus test results of their products.

Reputable Vender List

For that reason, it is important to be cautious when choosing your solar eclipse viewers and only purchase the glasses from authorized and credible manufacturers. You can find a list of reputable vendors from the AAS. The list was compiled after checking the ISO paperwork of every manufacturer to make sure the documents are in order, and the product was tested in an authorized facility. Moreover, every manufacturer listed their authorized dealers and resellers to make sure that people have access to a wide range of sources where to get their eclipse viewers. If the AAS does not list the vendor, that means the Society did not contact them, or their product was not deemed entirely safe for people to use.

What is the best way to find out whether your eclipse viewers are fake? Through a safe solar filter, no source of light which is the Sun itself or is comparable in brightness can be visible. The light sources comparable to the Sun include the reflection of the Sun in the mirror or shiny metal, an unfrosted incandescent, bright halogen, bright-white LED, bare compact fluorescent light bulbs, or an arc-welding torch. You can see these sources through a safe filter, but they will appear dim. However, if you see household light fixtures or anything else with ordinary brightness, you can question the quality of your solar viewer. Add to that a questionable vendor, and that makes it certainly unsafe.

Identifying Fake Solar Glasses

Quality eclipse glasses are designed to show the image of the sun clearly and comfortably bright against the dark sky surrounding it. So, when you use it, beware if your glasses shows the sun out of focus, too bright, or with a hazy background. That means the viewer is unsafe and poor quality. If you encounter a situation like that, make sure to return the product and demand reimbursement. Look up the list of reputable solar viewer manufacturers and get a quality replacement product.

Keep in mind that completely safe solar eclipse glasses only come from reputable manufacturers and meet ISO 12312-2 international safety standard. This is important because safe eclipse glasses not only makes it comfortable for you to look at the sun but also blocks UV and IR radiation to protect your health from their harmful effects.

If you have received solar eclipse glasses from an acquaintance or relative, and they are an astronomer, that means the product will be ISO compliant. That is because astronomers get eclipse glasses from well-known and reputable sources. Moreover, solar filters handed out by university astronomy and physics departments, amateur astronomy clubs, and professional astronomy organizations are also safe.

Science museums, planetariums, and astronomy trade shows also give out or sell ISO-compliant filters. If you are still not certain about their safety, being able to trace the product to a respected manufacturer and checking for the ISO logo and ISO 12312-2 compliance documentation is enough to prove that your glasses are good to go. Feel free to get your solar glasses from one of these sources, but never simply search for eclipse glasses on the web and end up buying the cheapest thing you see in ads.

Safely Viewing During Totality

It is believed to be perfectly safe to look at the sun without eclipse viewers during the phase of totality when the Moon blocks the Sun entirely. On July 2, 2019, totality will be visible in the provinces Buenos Aires, Cordoba, La Rioja, San Juan, San Luis, and Santa Fe and will take about 2 minutes and 30 seconds depending on location. The cities on the totality path include Rio Cuarto, San Juan, Villa Dolores, Dolores, Lujan, and Merlo.

If you are on the totality path, it is safe to look at the Sun without glasses only during the totality phase. However, before and after totality, and throughout the whole eclipse for those outside of the totality path, solar glasses are necessary for safety. The solar filters are sold as glasses or handheld cardboard viewers. It is not safe to use regular sunglasses to look directly at the Sun.

Here are updated instructions on how to use solar eclipse glasses and handheld viewers safely:

* Make sure to inspect your glasses or viewer before use. Check for any tears, scratches, or other damages and read the instructions that come with the packaging.
* Children can use solar filters only under adult supervision.
* Use your solar glasses over your regular eyeglasses if you normally wear them.
* Do not put on or remove your eclipse glasses while looking at the sun.
* Do not use any optical device like a camera or binoculars for looking at the Sun unless in a totality phase.
* Do not use any optical device for looking at the Sun while you are wearing your eclipse glasses or holding the viewer. The concentrated Sun rays could damage the solar filter and cause injury.
* If you want to use a solar filter with an optical device, consult an astronomer beforehand. Also, keep in mind that a solar filter should be attached to the front of the device.
* You can remove your solar filter only when the Moon completely covers the Sun if you are inside the totality path. Once the Sun begins to reappear, make sure to replace your solar viewer.
* Always use the solar viewer for looking at the Sun if you are outside of the totality path.

Today’s Solar Glasses

Before the ISO 12312-2 international safety standard’s adoption in 2015, solar viewers were only good for three years, and you could only use them for three minutes to look at the Sun. However, the filters designed today are very durable and, unless damaged, can be used indefinitely. Moreover, new eclipse glasses compliant with the ISO 12312-2 safety standard allow you to look at the eclipse as long as you want.

If you are looking to purchase a welding filter, keep in mind that only those filters of Shade 12 or higher are safe to use for directly viewing the sun. This shade is darker than most welding filters, so if you have a welder’s helmet, make sure you know the shade number of the filter before you use it to view the Sun. Shade 12 filter is the least dark you can use, but some people find it still leaving too much of the Sunlight to seep through. An ideal shade would be 13, although it is a rare find so you might want to try Shade 14 if the 12 is too bright.

You can also view the Sun in its partially eclipsed state indirectly through pinhole projection. For example, you can look at the shadow of a tree to see the Sun’s projection in the spaces between the leaves. As another option, you can face the Sun with your back and look at the shadow when you cross outstretched fingers of one hand over another. In both cases, you will see small crescent shadows projected by the Sun in its partially eclipsed state.


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