Is it safe to watch a solar eclipse without eye protection? A lunar eclipse?
Eye protection is not required during the totality phase of a solar eclipse or at any phase of a lunar eclipse.
It is very dangerous to view the Sun with the naked eye. It is even more dangerous to view the Sun through binoculars, a camera lens or a telescope. The Sun's light will burn the eye's retina painlessly and permanently!
The only time it is safe to view the Sun with the naked eye or through a lens is during the totality phase of a total eclipse. During totality, viewing the Sun with the naked eye or through a lens is the best way to enjoy the spectacle. I have seen 10 total eclipses!
If you want to view the Sun with the naked eye or through a lens you need a special filter. There are typically made of a metal film encased in mylar. The filters reduce the sunlight by a factor of one or two million. I have viewed the Sun through a mylar film with an 800mm lens with complete safety.
It is always safe to view a lunar eclipse with the naked eye. In fact you wouldn't see it through a filter.