eli5: Why did eclipse glasses say to only look at eclipse for 3 minutes at most, intermittently over a few hours.

Question

eli5:

I only saw this warning after I had looked through them for around 3 minutes (give or take a minute maybe, I’m not sure)

Now I’m anxious about whether they were even safe to use or not.

In: Biology

Answer 1

If you are using approved solar viewing glasses (per NASA, the ISO 12312-2 international safety standard) you can look at the sun for the entire time of the eclipse, every phase. As long as the glasses are not damaged and compliant with safety standards, there is not a specific time limit

If your glasses warn you not to look through them for more than 3 minutes, you are using old one that may not be compliant with modern safety standards in place for almost the last decade.

https://eclipse2017.nasa.gov/safety