A solar eclipse occurs when the moon blocks part of the sun. On Aug. 21, millions of people in the U.S. will experience a total solar eclipse pass over parts of North America as day turns to night. Houston will experience a partial solar eclipse. The last time this happened across the country was 1918. The partial eclipse will last two to three hours. Halfway through the event, there will be a brief total eclipse, viewable in certain states across the U.S.
Looking directly at a partial solar eclipse can cause irreversible eye damage, and even blindness. Sun damages vision permanently by burning the retina (light-sending tissue) of the eye, known as solar retinopathy. It’s important to have proper eye protection if you or your child plans to look at the eclipse. The only safe way to look directly at the sun is with special-purpose solar filters, such as eclipse glasses or handheld solar viewers. Be aware that ordinary sunglasses or homemade filters are not safe enough. It is also unsafe to use an unfiltered camera, telescope or binoculars to look at the uneclipsed or partially eclipsed sun, even when using eclipse glasses or handheld solar viewer.
There is one exception to this rule. During the total eclipse period, called “totality,” it is safe to look directly at the sun. This phase will last for about two minutes roughly within a 70 mile-wide path from Oregon to South Carolina. During this time, it is important to know when to take off and put the glasses back on. A total eclipse means the moon completely blocks the sun’s bright face, making visible the solar corona. Only those within the path of totality will be able to experience this. Other sky watchers will see a partial solar eclipse.
Even though Houston will only experience a partial eclipse, it is still necessary to use proper solar filters. The partial eclipse will begin around 11:45 am and end around 2:45 pm. The maximum eclipse in Houston will be around 1:15 pm.
The American Academy of Ophthalmology and the American Astronomical Society offer these five tips for viewing the eclipse:
- Be sure to use specially-designed solar eclipse glasses and viewers. There are four manufacturers that have certified their eclipse glasses and handheld solar viewers to meet the international standards: Rainbow Symphony, American Paper Optics, Thousand Oaks Optics and TSE 17.
- Don’t use your solar filter if it’s scratched or damaged.
- You can also view the eclipse through #14 welder’s glass.
- If viewing the eclipse through a camera lense, binocular or telescope, it must be fitted with the proper solar filter. Consult an astronomer.
- Do not use solar eclipse glasses to look through cameras, binoculars or telescopes – these devices concentrate the sun’s rays and damage the solar filter, allowing the sun’s rays to damage the retina.
According to the American Society of Retina Specialists, the following are unsafe solar filters:
- Looking through color camera film or black and white film such as negatives or x-rays
- Smoked glass
- Polarizing filters or neutral density films
A solar eclipse is a rare and striking spectacle. By carefully following these guidelines, it will be much more enjoyable. After the August 2017 eclipse, the next total solar eclipse will be in South America in July 2019.