Guidelines for Safe Viewing of August 12 Total Solar Eclipse
Experts advise using ISO-certified eclipse glasses or solar filters and warn against looking at the Sun with ordinary sunglasses or unfiltered optical devices.
A total solar eclipse will be visible on August 12 across parts of Greenland, Iceland, northern Russia, Spain and Portugal, with a partial eclipse observable in much of Europe, northwestern Africa, the northern United States and Canada. Observers in the path of totality will experience a complete blockage of the Sun, while those outside will see only a partial obscuration.
NASA and other scientific bodies stress that the only safe time to view the Sun without protection is during the brief period of totality. Outside that window, even a small visible portion of the Sun can cause permanent retinal damage. The Institute of Astrophysics of the Canary Islands notes that the remaining 1% of the Sun’s surface still emits enough radiation to harm the eye’s light-sensitive cells.
To watch the eclipse safely, viewers should wear glasses that meet the ISO 12312-2 standard or use a handheld solar viewer. These filters block visible, infrared and ultraviolet light and are roughly 100,000 times darker than regular sunglasses, which are not designed for direct solar observation. The American Astronomical Society recommends checking its curated list of certified manufacturers for reliable products.
"Put on your eclipse glasses before looking up and remember to turn away from the sun before you remove them again," the society advises, adding that children should be supervised at all times.
Optical devices such as telescopes, binoculars or cameras must have an appropriate solar filter on the front; using them without a filter, even with eclipse glasses, can allow concentrated solar rays to damage the eyes. Welding filters with a shade number of 12 or higher are also acceptable, though auto-darkening helmets are not recommended because they may not react quickly enough.
Certified eclipse glasses do not expire as long as they remain undamaged, and they can be stored for future events. Cleaning should be done with a dry tissue or cloth, avoiding liquids that could weaken the frame.
For those without certified glasses, indirect methods such as pinhole projectors made from cardboard, colanders or even the gaps between leaves can project a safe image of the eclipse onto a surface. Direct viewing through a pinhole or looking at the Sun is prohibited.