To safely view a solar eclipse, it is important to use proper eye protection. The most common way to do this is by using solar eclipse glasses or handheld solar viewers that meet the ISO 12312-2 international safety standard. These glasses and viewers are made with lenses that are made of black polymer, a flexible resin infused with carbon particles, that block nearly all visible, infrared, and ultraviolet light. It is important to avoid using ordinary sunglasses, neutral density or polarizing filters, smoked glass, photographic or X-ray film, or space blankets, as these do not provide adequate protection.

When purchasing solar eclipse glasses or handheld solar viewers, it is important to buy from reputable sellers that have been approved by the American Astronomical Society. Some counterfeit glasses have been sold in the past, so it is important to check that the glasses are ISO-compliant and meet current safety standards. It is also important to check that the glasses are not scratched, punctured, torn, or coming loose from their frames, and to replace them if they are.

To test if a pair of eclipse glasses is safe, you can try looking at bright objects other than the Sun, such as a shaded lamp in your home. If you can see the light, the glasses are not strong enough. If you cant see the light, try looking at something brighter like a bare lightbulb. This should appear dim through a safe solar lens. If that works, you can try glancing at the Sun through your eclipse glasses. If you find it uncomfortably bright, out of focus, and/or surrounded by a bright haze, this is another sign that your eclipse glasses aren’t safe.

In summary, to safely view a solar eclipse, use solar eclipse glasses or handheld solar viewers that meet the ISO 12312-2 international safety standard, and buy them from reputable sellers that have been approved by the American Astronomical Society.