How to enjoy a solar eclipse in total safety

The first rule of a solar eclipse is, you don’t look directly at the sun with the naked eye. The second rule of a solar eclipse is, you don’t look directly at the sun with the naked eye. 

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Por Maria Lazarte
Etiquetado como SeguridadMedio ambiente
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If you value your eye sight, you can admire this astronomical event in all safety with a pair of protective glasses conforming to ISO 12312-2:2015, Eye and face protection – Sunglasses and related eyewear – Part 2: Filters for direct observation of the sun.

21 August, 2017 – Total eclipse

A total eclipse of the sun will take place on 21 August. Anyone in the path of totality, which will cross the United States from West to East, will be able to enjoy the full experience, with many other areas in North America and elsewhere observing a partial eclipse. In view of this event, we have received numerous questions regarding ISO 12312-2. Here are some answers to your most common concerns.

What happens if you look at the sun with the naked-eye during a solar eclipse?

If you do not follow safety advice when experiencing a solar eclipse you could temporary or permanently damage your eyes. The primary concern is “eclipse blindness” or retinal burns caused by exposure to intense visible light that damages or even destroys the ability of our cells to respond to visual stimulus.

In order to prevent this, you can wear a pair of protective glasses designed specifically to view a solar eclipse, complying with ISO 12312-2:2015. Every day sunglasses are not enough. Using dark materials to create homemade filters will not protect you either.

The only time that the sun can be viewed with the naked eye is when the moon completely covers the disk of the sun during a total eclipse. It’s never safe to look at a partial eclipse or at any of the in-between stages of a total eclipse. Even if 99 % of the sun is obscured, the remaining sun can still cause retinal burn.

What does ISO 12312-2 say?

This part of ISO 12312 applies to all afocal (plano power) products intended for direct observation of the sun, such as solar eclipse viewing.

The standard provides safety requirements and test methods. It also requires the following information to be included with the product:

  • Name and address of the manufacturer
  • Instructions for use
  • Warnings that viewing the sun without an appropriate filter can result in injury
  • Warnings that damaged filters should be discarded
  • Advice on storage, cleaning and maintenance
  • Obsolescence deadline

The sun can only be viewed with filters specially designed to protect the eyes. They should adequately cover all the visual area of both eyes simultaneously.

The filters are specifically designed to protect from visible, ultraviolet and infrared radiation. Most of these have a thin layer of chromium alloy or aluminum that attenuates visible and near-infrared radiation. One of the most widely available filters is shade 14 welder’s glass, which you can find in welding supply outlets. Another alternative is aluminized polyester that has been specially designed for solar observation, or “black polymer” in which carbon particles are suspended in a resin matrix.

How can you tell if a pair of glasses conforms to ISO 12312-2?

The reference to the standard should be included at least on the packaging. Although ISO develops standards, we do not certify or verify products (conformity assessment). This is done by third-party bodies. To find out if your glasses are safe, please read the advice of the ISO member for the USA, ANSI.

Can I put the sunglasses on a telescope or other viewing device?

No. Sunglasses for viewing solar eclipses should only be used as intended. If you are using a camera, telescope or binocular, you need especially designed filters for your devices. Preferably invest in a good quality filter, as cheaper ones may crack unexpectedly from overheating. Homemade filters like for example “black” developed film or smoked glass will not work.  

Does ISO make solar eclipse sunglasses?

No. We only make standards that manufacturers can comply to.

Maria Lazarte
Maria Lazarte

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