Space.com:

Solar eclipses such as annular eclipse on Sunday can be treacherous for the inexperienced. A ring (“annulus”) of the sun’s disk remains in view even at the moment of maximum coverage by the moon. Your eye’s iris will be fooled by the relative darkness of the moon’s silhouette. But dangerous direct sunlight appears around the edges and can hurt you badly without precautions.Experienced eclipse chasers watching a total solar eclipse will have a short time — during totality only — when they may view the eclipse directly. Don’t try this unless you are with someone who has done it before and can still see. But don’t try it at all under Sunday’s annular solar eclipse.If you’re planning to watch a solar eclipse or look for sunspots, what is the proper optical filter material for sun-watching?