This month sees the return of a rare astronomical phenomenon. The total solar eclipse on Monday, August 21st will turn day into night from coast to coast across the United States. The path of the full eclipse will cover from Oregon to South Carolina, areas where, at totality, the sun will appear to be completely blocked by the face of the moon. Those outside of the direct path of the moon’s shadow will see the eclipse as a partial solar eclipse, but either experience will be an event that is not to be missed.

The last total solar eclipse crossing the entire United States was in 1918. As the moon moves between the Earth and the Sun, the sky will begin to darken, and at its peak, celestial bodies, such as planets and some of the brightest stars, may become visible. The solar atmosphere—the corona—will also be visible, and as its name implies, a halo of light resembling a crown radiating with swirls and jets of solar energy will appear as well.

In order to safely view an object as bright as the sun, special filters must be used. Looking at the sun directly with the naked eye—even for a few seconds—can cause eye damage and possibly blindness. NASA states that at the moment of the sun’s total eclipse behind the moon, it is safe to view the sun without protection, but using special eclipse filters will be necessary to know when that moment of totality occurs.

Never look directly at the sun unprotected. Special disposable glasses can be purchased or ordered with dark filters specifically made for solar viewing. These filters block thousands of times more light and are more specialized than ordinary sunglasses or tinted lenses. DO NOT attempt to view the sun with ordinary sunglasses. The American Astronomical Society (AAS) has recommended that any filters or “eclipse glasses” used for viewing the eclipse meet or exceed ISO 12312-2 standards regulating these devices.

In addition, even with the appropriate eclipse glasses, DO NOT look at the sun through binoculars, cameras, or any other magnifying lens. Eclipse glasses are not designed for viewing the sun under refraction. There are filters for telescopes and camera lenses that filter out even more of the damaging bright rays, but these will be specific to the application platform.

A complete list of reputable vendors selling ISO compliant filters is available at the AAS’ website; some retail chains, like 7-Eleven, Best Buy, REI, Toys “R” Us, and Walmart, are included.

If eclipse glasses are not available or if you live outside the path of the total solar eclipse but you don’t want to miss out, NASA will also broadcast the eclipse live. This “Eclipse Megacast” will be online, picked up locally and nationally on television, or it can be viewed directly on NASA’s website.

Experts will explain the eclipse as it is happening and special cameras displaying multiple eclipse phenomenon from earth and space with scientists and the public interacting will be broadcast for the four hours surrounding the eclipse on August 21, 2017.