It’s the most awe-inspiring event off the planet Earth, that we can see from Earth.
And the last time it happened in North America, Jimmy Carter was president of the United States, the Soviet Union had not yet invaded Afghanistan and Christina Aguilera’s first number-one single, “Genie in a Bottle,” topped the Billboard hits chart.
It’s set for August 21, 2017: the next total solar eclipse.
It will pass over the United States from Oregon (beginning at 10:15 AM local time) just north of Newport to South Carolina, leaving the US coastline at 2:36 PM local time. The path of totality, or umbra, where you will see a total eclipse will be about 67 miles wide. This site maps it out for you. Outside the umbra there is a wider area, the penumbra, where people see only a partial eclipse.
People are already booking hotel rooms.
Everybody wants to see the solar eclipse, but make certain you watch it safely.
The Danger of Sunlight
During normal circumstances the sun is so bright you instinctively never look directly at it. It’s painful, and that’s good, because just a few seconds of exposure permanently damages your eye’s retina. That’s because the Sun radiates intense visible and invisible light. If it goes directly into your eye, your lens focuses it into a beam of heat that burns a hole in your retina.
The Danger of Solar Eclipses
The problem with viewing solar eclipses is that the Sun’s light is so bright, it is dangerous to look directly at even a small fraction. However, because the light is abnormally diminished, you feel as though it’s twilight and, therefore, safe. That feeling of eye safety is an illusion.
It is never safe to look directly at the sun when any portion of its disk is visible, even just 1%.
It is safe to view the total phase of a total solar eclipse with the naked eye, but don’t push it. That phase lasts only a few minutes.
During a solar eclipse the Moon is moving across the Sun. When it fully blocks the Sun, it is safe to look at the sun. However, before and after that happens, the Moon only partially blocks the Sun. When the Moon’s edge first covers the Sun’s is known as first contact. From that point on, the Moon progressively moves in front of the Sun and, consequently, the air around grows darker. This period lasts about one hour.
Continue to protect your eyes. During this partial period of the eclipse, looking directly at the sun is not safe without proper filters.
When the Moon completely covers the Sun, your area turns dark as night. You can even see stars and planets. This is the period of the totality, and is the only time when it’s safe to look directly at the Sun without protection. However, remain alert and careful. This lasts only a few minutes. If you’re in an area organized for eclipse viewing, wait until somebody blows a whistle to signal the onset of totality.
The Moon keeps moving east, and so, after totality, will take about another hour to entirely uncover the Sun. Protect your eyes.
Therefore, for your eye safety, you must use special eclipse safety glasses to view the Moon as it crosses and uncrosses the Sun. NASA clearly explains this.
If You’re Not in the Path of Totality
You will experience a partial solar eclipse, never the totality. Keep your protective eclipse glasses on from first to last contact. There is no point at which it’s safe for you to look directly at the Sun.
The only safe way to view a solar eclipse when it’s not a total eclipse and you’re not at the totality is through the proper filters.
These filters have a thin layer of chromium, aluminum or silver which attenuates the visible, infrared and ultraviolet ranges of the light spectrum. Number or Shade 14 welders glasses available from welding supply outlets are the most common source. Some use aluminized mylar.
Do not wear sunglasses. They do not provide enough protection.
Do not wait until the last moment to buy glasses from dealers at eclipse viewing sites. You will probably pay too much money. More importantly, you are trusting your eyesight to someone you do not know and will never see again. If they sell you protective glasses that are too weak to protect your eyes during the partial phases of the eclipse, “not see them again” might become the literal truth.
Buy your solar eclipse glasses from reputable dealers selling glasses from reputable manufacturers. Look for established companies that have a well-earned reputation in the industry. Solar eclipse glasses are not usually in large demand, so look for companies that sell protective glasses for other uses. These includes:
* Safety glasses
* Military uses
Solar eclipse glasses manufactured by a company experienced with making such safety glasses will protect your eyes better than those sold by somebody just trying to take advantage of the eclipse and the temporary demand it’s creating.
Solar Eclipse Glasses Standards
* Block 99% of ultraviolet light
* Block 97% of infrared light
* Number or Shade 14 welders glasses
* If you buy your eclipse glasses in or from Europe, make certain the manufacturer marked them CE certified. That means they meet the safety requirements of the European Union.
Cameras, Binoculars and Telescopes
Cameras are not made for pointing directly at the Sun. That can seriously damage the lens of your equipment just as it would your eye. If you want to photograph the eclipse, check with the manufacturer for the special equipment or filters needed.
Do not look directly at the sun through a camera even if you are wearing eclipse glasses. That’s because the camera lens magnifies the sunlight so that it’s so strong even the Shade 14 glasses can’t protect your retinas.
That’s also true of binoculars and telescopes. Do not point them directly at the sun and look into them, ever.
Do not use any filter with any optical device unless that filter was expressly made for that purpose.
Total solar eclipses are exciting events reminding us of the incredible, vast universe we occupy. Everybody should experience one. However, it’s not worth your eyesight for the rest of your life. Buy your solar eclipse glasses in advance from a reputable source with experience and a reputation you can count on. If you miss the one in 2017, you can always catch the next one to hit North America in 2024.
Contact us with any questions about use glasses and filters to protect your eyes.