Solar eclipse 2017: How to watch without permanently damaging your eyes

People look through eclipse viewing glasses, telescopes or photo cameras an annular solar eclipse, on September 1, 2016, in Saint-Louis, on the Indian Ocean island of La Reunion. Richard Bouhet/AFP/Getty Images

On Aug. 21, millions of eyes across North America will be glued to the sky in anticipation of a solar eclipse.

The natural phenomenon, during which the moon blocks the sun, will last up to three hours in total, according to NASA. But those wanting to catch a glimpse will have to be quick. As it rotates, the eclipse will only last at each location about two minutes and 40 seconds.

WATCH: Solar eclipse to cut across entire U.S. on Aug. 21

Click to play video: 'Solar eclipse to cut across entire U.S. on Aug. 21'
Solar eclipse to cut across entire U.S. on Aug. 21

NASA is also warning viewers to keep safety in mind. The space agency released a statement explaining “eclipse viewing glasses” or “handheld solar viewers” must be used. Staring directly at the eclipse can damage retinas.

Story continues below advertisement

“It’s common sense not to stare directly at the sun with your naked eyes or risk damaging your vision, and that advice holds true for a partially eclipsed sun,” the agency stated.

READ MORE: What Canadians can expect during the solar eclipse on August 21

The organization went on to explain that eye gear must have certification, with a “designated ISO 12312-2 international standard.” The company who created the product and its contact information should be clearly printed on the glasses.

It warned that glasses older than three years, or with scratches, should not be used. Ordinary sunglasses — even dark ones — and homemade contraptions aren’t sufficient.

In this May 20, 2012, file photo, the annular solar eclipse is seen as the sun sets behind the Rocky Mountains from downtown Denver. David Zalubowski/AP

Certified eclipse glasses make sure no more than 0.00032 per cent of sunlight is transmitted to the eyes, according to Regular sunglasses only protect the eyes from a fraction of sunlight, and are made of different material.

Story continues below advertisement

READ MORE: NASA to use 11 different spacecraft to measure the sun during solar eclipse

Sunglasses are usually made from plastic or glass, whereas eclipse glasses are usually made from polyester film, and then coated in black polymer.

Those who want to purchase the special glasses can buy them online. The price range varies, but begins at just a couple of dollars.

The eclipse will be visible in several parts of Canada.

Those in Vancouver will be able to view nearly 90 per cent of the sun go dark around 10 a.m. PT. The eclipse will cover over 80 per cent of the sun in Regina, about 70 per cent in Edmonton, Winnipeg and Toronto.

In Ottawa and Montreal, the eclipse will cover 60 to 70 per cent, while in Quebec City, Halifax and St. John’s, it will cover 60 per cent.

Story continues below advertisement

 NASA will livestream the event for those who can’t catch the eclipse in real life.

— With a file from Global News reporter Monique Scotti  

Sponsored content