A total solar eclipse visible in the United States is rare – and precious, just like your vision. When the moon crosses in front of the sun skies will darken, stars will twinkle and millions of Americans will be treated to an astronomical show.
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The only safe way to look directly at the sun is through special-purpose solar filters, according to the American Academy of Ophthalmology. These special filters are used in eclipse glasses and hand-held solar viewers. Eclipse glasses are available for purchase at big-box stores, electronics supply outlets and online. Look for glasses that carry this certification insignia: ISO 12312-2.
"The concern over improper viewing of the sun during an eclipse is for the development of 'eclipse blindness' or retinal burns," said associate professor of optometry Dr. Ralph Chou in an article published by the National Aeronautics and Space Administration.
Chou said children and young adults are most at risk as bright light and radiation from the sun can cause heating and cook the exposed tissue of the eye. The aging process can provide a natural filtering effect in older people and reduce risk of retinal damage.
NASA outlines do's and don'ts of viewing the eclipse:
• Do not look directly at the sun
• Do not use homemade filters or ordinary sunglasses, even very dark sunglasses
• Use special solar filters, such as eclipse glasses or handheld solar viewers, to view the eclipse
• Read and follow filter instructions and supervise children
• In any stage of eclipse, do not look at the sun through a camera, telescope, binoculars or other optical device, and never use solar filters with these devices, as concentrated solar rays will damage them and can cause serious eye injury
• Inspect your solar filter before use; if it is scratched or damaged, discard the filter
• Pinhole projection is a safe way to view the sun in indirect fashion; Exploratorium provides instruction on "How to Build a Sun Viewer" and other methods of safely viewing the sun
The range is from two to seven eclipses each year, according to EarthSky.
• One calendar year has a minimum of four eclipses, two solar and two lunar
• The last time there were seven eclipses in a single year was 1982, and the next time will be 2038
• Few people see the shallow solar eclipses that occur regularly in the Arctic and Antarctic regions