During a total solar eclipse, astronomers warn that safe viewing without protective glasses is limited to totality, when the Moon completely covers the Sun’s bright surface. Only then can viewers see the corona, the white halo surrounding the darkened Sun, with the naked eye. The American Astronomical Society (AAS) and NASA distinguish this brief interval from the partial phases: certified eclipse glasses must stay on until totality begins.
Eye damage remains a risk if glasses come off before the last bright sunlight disappears or are not put back on as soon as sunlight returns. The first bright bead of sunlight marks the end of totality and the moment to restore protection. Viewers should use eclipse glasses or handheld solar viewers that meet ISO 12312-2, the standard for filters intended for direct solar viewing. Ordinary sunglasses, including dark or polarized pairs, are no substitute. Scratched or torn glasses should not be used; neither should glasses with punctures or other damage.
To coordinate these critical transitions, astronomers recommend having one person guide a group and announce when to remove and replace glasses. The approach resembles the tradition of eating grapes at New Year’s: a shared sequence helps everyone act at the right time. Jorge Pérez Gallego, director of communication and outreach at the US National Solar Observatory, coordinated the scientific broadcast for the 2024 eclipse and has highlighted the value of this coordinated approach.
Optical equipment requires a separate precaution. Binoculars and cameras concentrate sunlight; telescopes pose the same hazard. Eclipse glasses worn behind an unfiltered instrument do not provide adequate protection. A purpose-built solar filter must be securely fitted over the front aperture. As noted in a recent report on the strict rules for eclipse viewing in Spain, even a brief lapse in protection can cause lasting eye injury.
The naked-eye exception applies only to a total solar eclipse and only to observers within the path of totality. During an annular eclipse, the Moon appears smaller than the Sun, leaving a bright ring visible throughout the basic phase; protection must stay on for the entire event. At public gatherings, a designated announcer can help spectators follow the transitions into and out of totality while keeping certified viewers in place during every partial phase.
