How long can you look through eclipse glasses? On and off: what the IGN and the AAS say

On and off. The IGN (Spain’s National Geographic Institute) writes that eclipse glasses are designed for looking at the Sun “for short periods of time, well under a minute”, and the official Trío de Eclipses website, run by the Spanish government for the three eclipses, asks you to look for a few seconds, lower your eyes and never go beyond three minutes in a row. The American Astronomical Society (AAS) sets no limit: with glasses that meet ISO 12312-2 and are in good condition, it says, you can look at the partially eclipsed Sun for as long as you like. As the partial phase lasts more than two hours (in Ceuta, from 09:41:02 to 12:01:09 Spanish time, CEST, UTC+2), looking on and off keeps everyone’s advice and you miss nothing.

What the IGN says

On its page about how to observe eclipses, the IGN explains that “eclipse glasses” “are designed to observe the Sun safely for short periods of time, well under a minute”. It sets two conditions: that they are in good condition, “without scrapes, perforations, scratches, breaks or folds”, and that they are tested beforehand by looking at an incandescent light bulb.

On the same page it gives a reason not to drag out each look. It considers observing the Sun, “even with a good filter”, to be “somewhat dangerous, because a moment’s distraction can end with you looking without that filter”, and gives the example of a child who has the filter in front of their eyes and moves it aside to take a peek. The longer you spend with your eyes fixed on the Sun, the more chances there are for that kind of slip.

What Spain’s Health Ministry and the government website ask

Spain’s Ministry of Health put it in writing in its risk assessment for the Trío de Eclipses, which also covers the 2027 eclipse: “It is important that observations are brief and intermittent”. The official Trío website turns that into a routine. You put the glasses on before looking at the Sun, “look briefly for a few seconds and lower your gaze”, repeat the observation “always with breaks” and “never” look “for more than three minutes in a row”. The glasses come off only after you have looked away from the Sun.

What the AAS says

For the AAS, what counts is the condition of the glasses. If the manufacturer had them tested by an accredited laboratory that confirmed they meet ISO 12312-2, and the filters are not scratched, punctured, torn, coming away from the frame or damaged in any other way, you can look through them at the uneclipsed, partially eclipsed or annularly eclipsed Sun for as long as you like. It considers the warnings printed on some glasses (don’t look for more than three minutes at a time) outdated for glasses recently made to the standard and in perfect condition.

Its way of using them also works in turns: standing still, you cover your eyes with the glasses before looking up at the Sun; when you have finished, you look away and only then take them off, never while you are looking at the Sun. The AAS is talking about what a good filter can withstand; the IGN, the Health Ministry and the Trío website, about how best to use it.

Two hours and more of partial eclipse

The Moon moves slowly. With a glance of a few seconds every few minutes you can watch the bite grow, and in between there is plenty to see without looking at the Sun: we cover it in what to do during the eclipse. The times for where you are, in when is it?.

Inside the path of totality there is a stretch when you don’t need the glasses, from the moment the last flash goes out until the first one appears. In Ceuta, the cautious window runs from 10:45:19 to 10:50:01; each municipality’s is in when to take off your eclipse glasses in totality. Outside the path there is no moment without glasses, and why you shouldn’t go even a second without them is explained in don’t look at the partial phase without glasses (in Spanish).

With children

The AAS asks for children using solar filters to be supervised at all times, and the Health Ministry’s assessment insists on “close supervision of minors to ensure the correct and continuous use of eye protection”. In practice, an adult decides when the child looks and for how long, checks that the glasses don’t slip and is right there when they come off, which is exactly the moment of distraction the IGN warns about. Sizes and tricks to keep them in place, in eclipse glasses for children.

If you have a pair from last summer’s eclipse, check them before using them: we explain how in do eclipse glasses expire? (in Spanish). On Order your glasses you can ask for ours: cardboard, with the EN ISO 12312-2 certificate, along with the phone filter and packs for groups. To check any other pair, see our glasses guide.

Sources: IGN — Cómo observar los eclipses (in Spanish: glasses for periods “well under a minute”, their condition, the light-bulb test and the risk of a moment’s distraction); Ministerio de Sanidad — Evaluación rápida de riesgo del Trío de Eclipses (Spain’s Ministry of Health, rapid risk assessment, in Spanish: “brief and intermittent” observations and close supervision of minors); Trío de Eclipses, web oficial del Gobierno — Salud visual (the Spanish government’s official website, in Spanish: a few seconds, breaks, never more than three minutes in a row, taking them off after looking away); AAS — How to View a Solar Eclipse Safely (no time limit with ISO 12312-2 glasses in good condition, the three-minute warnings outdated, how to put them on and take them off, supervising children); start, end and totality times: eclipseando data (skyfield + DE440s engine), cross-checked against the IGN’s times.