How to watch the eclipse safely in Ceuta
ISO 12312-2 filters, the mistakes people make, and the only safe moment to look without glasses during the 2 August 2027 eclipse in Ceuta.
A solar eclipse is the only mass astronomical event that can leave permanent damage in people who watch it wrongly. The retina has no pain receptors, so the injury gives no warning: central vision loss appears hours later and often does not recover. Everything below comes down to one rule: in Ceuta, throughout the entire partial phase, a certified filter with no exceptions.
Which filters work and which do not
Only filters meeting the international standard ISO 12312-2 are safe. They cut visible light by a factor of around one hundred thousand and also block infrared and ultraviolet. They come in two forms: cardboard eclipse glasses and sheets of solar filter for instruments.
- Safe: eclipse glasses marked ISO 12312-2 with an identifiable manufacturer, and glass or film solar filters fitted in front of a telescope objective.
- Not safe: sunglasses of any category, smoked glass, X-ray film, photographic negatives, CDs, dark glass bottles, or welding filters below shade 14.
- Never: looking through a telescope, binoculars or telephoto lens with the filter behind the eyepiece. The concentrated heat destroys it and the light reaches your eye directly.
The ten-second check
The only moment you can look without a filter
During totality, and only during totality. In Ceuta that means about 4 min 48 s, between 10:45:17 and 10:50:06 local time. In that window you look with the naked eye, no filter, and it is the only way to see the corona: through eclipse glasses you would see nothing at all.
Trust the Sun, not the clock
Watching with children
- One adult per small child during the partial phase: the glasses slip, and a child's instinct is to look up.
- Projection is the zero-risk alternative: a kitchen colander or a card with a pinhole throws dozens of crescent Suns onto the ground.
- Explain what will happen beforehand. The drop in light and temperature during totality is startling, and it is better not to be a surprise.
Checking a pair before you use them
- Hold the filter up to a light and look for scratches, pinholes or creases. Any defect makes them useless.
- Check the filter is firmly attached to the frame and not lifting at a corner.
- Put them on in a lit room: you should see nothing except the brightest lights.
- Look for ISO 12312-2 and a manufacturer's name printed on them. No manufacturer means nobody is accountable.
Where to get them
Planetariums, astronomy societies, opticians and telescope shops usually distribute them in the months beforehand, and many town councils inside the path hand out free batches. Avoid unbranded street sellers in the final days, which is when counterfeit stock appears. If you are travelling from abroad, buy from a recognised supplier at home and bring them with you rather than relying on finding stock on arrival.
Will ordinary sunglasses work for the eclipse?
No. Sunglasses, even category 4 ones, let through thousands of times more light than the eye can tolerate when looking directly at the Sun. Only filters certified to ISO 12312-2 are safe.
Can I look without a filter during totality?
Yes, and it is the only moment when you should: during totality the solar disc is completely covered and the corona is only visible to the naked eye. The instant the first point of light reappears, the filter goes straight back on.
Can I photograph the eclipse with my phone?
Pointing a phone camera at the Sun without a filter can damage the sensor during the partial phase, and looking at the screen does not protect your eyes if you glance at the Sun. The partial phase needs a solar filter in front of the lens; during totality you can shoot without one.
How do I know if my eclipse glasses are genuine?
They must be printed with a reference to ISO 12312-2 and an identifiable manufacturer. With them on you should see absolutely nothing except the filament of a very bright bulb or the Sun itself. If you can make out shapes in the room, they are not safe. Be wary of unbranded glasses sold loose in the days before.
Do eclipse glasses expire?
The filter material does not expire on its own, but it does get damaged. The practical rule is to discard any pair with scratches, pinholes, creases in the filter, or a filter coming away from the frame. If in doubt, do not use them: they cost very little and a retina cannot be replaced.
Is it safe for children?
Yes, with supervision. One adult per small child during the partial phase is sensible, because the glasses slip. For very young children, projecting the Sun through a kitchen colander or a card with a pinhole is a completely risk-free alternative.