With only days to go until the solar eclipse on 8 April, experts are warning the public to beware of fake solar glasses on the market.
According to Hin Cheung, a clinical assistant professor at the Indiana University School of Optometry: 'If you were to use a fake viewer that does not meet that [ISO] standard, then unsafe levels of solar radiation could enter your eye and cause damage.
'That damage could also cause permanent changes to your vision.'
Eclipse totality lasts 3.5 to 5.5 minutes. It's never safe to directly look at a partial eclipse directly without a special eye guard.
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To avoid eye damage and ensure you have a legit set of solar viewers, make sure to check these steps.
Astronomer and science communicator Rick Fienberg created a list of verified solar filters and viewers that protect wearers’ eyes.
In early March, Fienberg noticed the increase in fake solar glasses.
Around the solar eclipse event in 2017, Fienberg and his team spotted some counterfeit glasses entering the marketplace.
To make sure your glasses are real, Cheung recommends that people check out the AAS list of legitimate solar viewers.
Anyone can print an ISO number and claim their safety, however, this list is the best way to determine the authorisation of the viewers.
Meanwhile, Cheung says to ignore glasses are 'NASA-approved' as the space agency does not endorse commercial products.
Before the event, make sure your solar viewers don't have any scratches or tears and that you don't look directly at the sun.
Fienberg also described that there's a quick three part test you can do to see if your solar viewers work as they should.
First, try on your glasses indoors and look around.
Legitimate eclipse glasses are 1,000 times darker than the darkest sunglasses you can buy so you should only be able to see very bright lights like a smartphone flashlight or a halogen bulb.
If this works, then try the same outdoors without looking at the sun. The filter should make it too dark to see any hills or trees, especially in the distance.
After this, it's time to test it out on the Sun. Briefly glance at the Sun and you should comfortably see a bright, sharp-edged circular disk.
If your glasses pass all these tests, they are likely safe to wear.
When it comes to the event, Fienberg points out to use the glasses for only a few seconds every minute or so during the eclipse as they're intended to be used.