By Christopher Brady, MD, an ophthalmologist at the University of Vermont Medical Center and assistant professor at the Larner College of Medicine at UVM. (This blog was reprinted by permission from the University of Vermont Medical Center HealthSource blog.)
On August 20 I’m taking my six-year-old daughter to Nashville, Tennessee to see the Great American Eclipse. This is the first eclipse to sweep across both coasts of the United States in 99 years. A partial eclipse will be visible in Vermont, peaking at 2:40 p.m. on Monday August 21. To see the moon completely block out the sun’s light, you’ll need to travel to the path of “totality.”
What is a Solar Eclipse?
A solar eclipse is a truly spectacular phenomenon. Everyone should try to catch a glimpse of this unique event. Whether you stay here or travel, eye safety is of the utmost importance. During the minute or so of totality, it is safe to look at the sun without any protection or special filter, but that will not be possible in Vermont.
The energy from the sun’s light can cause permanent damage to the very sensitive tissue in the eye called the retina. Solar retinopathy is the name given to the problems caused by looking at the sun. It is a well-known problem to all retina doctors. In fact, the eye is designed to focus light on a very tiny portion of the retina. Looking at the sun directly is like focusing a magnifying glass on a dry leaf. Think of that image if you are tempted to look at the sun without protection!
How to Keep Your Eyes Safe
Here is how to view the eclipse safely:
- Get a free pair of “eclipse glasses” from your local library or an inexpensive pair on the internet. My daughters picked up some paper and plastic glasses from the local library, but supplies may be limited and run out. Get these glasses from a reputable source, because there have been reports of counterfeit glasses being sold. The American Astronomical Society has guidelines.
- Watch the eclipse indirectly. You can do this with something as simple as a pinhole poked through aluminum foil.
- Modify existing binoculars, a camera or telescope with a solar filter. I do not recommend this method unless you plan to do more research and practice so you can do this safely. The most important point is: Whatever you use, you must put your solar filter in FRONT of your device. Remember the image of the magnifying glass and the dry leaf? Your camera, binoculars or telescope also focus the intense energy of the sun and can burn through the filter (and your retina) if you put the filter over the eyepiece.
There are a couple of things to avoid:
- Regular sunglasses, polarized sunglasses, and even most welding glasses do not block enough light to make it safe. The appropriate glasses block about 100,000 times more light than normal sunglasses!
- Using film. There are techniques described on the Internet to make a safe filter, but I would not recommend this given that real filter paper is not expensive or hard to come by.
Get Ready for the Next Eclipse in 2024!
I hope you are as excited about the Great American Eclipse as I am. Wherever you are, be sure to watch safely. If you aren’t traveling to the path of totality this year, don’t worry, in seven short years, on April 8, 2024, another solar eclipse will occur, and the path of totality will pass right through northern New York state and New England.
More information about viewing the eclipse safely and solar eclipse glasses and filters are listed below:
Christopher Brady, MD, is an ophthalmologist at the University of Vermont Medical Center and assistant professor at the Larner College of Medicine at UVM.