Another way is Hydrogen-alpha (Hα) filters, which instead of sunspots show prominences and other details on the sun's surface. Hα filters do that by only allowing through light from hydrogen atoms.

The Smar Solar Filter only transmits 1/100,000th of the sun’s light, making it safe to view through the telescope’s eyepiece. You can also safely gaze at the sun via your phone or tablet using the ...

As soon as the sun starts to re-emerge, the glasses need to immediately go back on. "It is possible to observe the eclipse in perfect safety," says Chou, who has seen 19 total solar eclipses.

The sun filter is absolutely necessary both for solar viewing and for eclipse viewing. I'll spare you the lecture about why you shouldn't look at the eclipse without specialized equipment, but ...