How to safely view the Sun
Never through an instrument without a front-fitted solar filter. Never with anything that isn't certified. No exceptions but one.
5 min read · Published 24 August 2026
In one paragraph
Never look at the Sun through any optical instrument without a filter designed for solar viewing and fitted at the front. Use ISO 12312-2 certified eclipse glasses for naked-eye viewing, or a purpose-made solar filter over the aperture of a telescope or binoculars. Sunglasses, exposed film, smoked glass and welding glass below shade 14 are all unsafe. The one exception is totality during a total solar eclipse, when the Sun's disc is fully covered.
Why it is dangerous in a way that feels safe
The retina has no pain receptors. Damage from looking at the Sun produces no sensation at the time. Symptoms show up hours later: a blurred or dark patch in the centre of your vision.
That delay is the whole problem. Every instinct that stops you touching something hot is missing here. The feedback that would make you stop doesn't exist.
The condition is solar retinopathy. It can be partial and it can be permanent, and it hits central vision, the part you read and recognise faces with. Cases spike after every widely publicised eclipse.
If the glasses aren't certified, throw them away. I'd rather miss an eclipse than trust a market-stall pair.
What is safe
| Method | Safe? | Notes |
|---|---|---|
| ISO 12312-2 eclipse glasses | Yes | For naked-eye use only. Check for damage before each use |
| Front-mounted solar filter | Yes | Must cover the full aperture and be securely attached |
| Solar projection | Yes | Project the image onto card, safest method for groups |
| Pinhole projection | Yes | A hole in card projecting onto a second card. Free and completely safe |
| Purpose-built solar telescope | Yes | Hydrogen-alpha instruments show prominences and detail |
| Eyepiece 'sun filter' | No | Old accessory that can crack from concentrated heat. Discard any you find |
| Sunglasses, even stacked | No | Nowhere near sufficient |
| Exposed film, CDs, smoked glass | No | Do not block infrared reliably |
| Welding glass below shade 14 | No | Shade 14 or higher only |
| A phone camera to 'check' | No | You still look at the Sun to aim it, and it can damage the sensor |
The projection method
The safest approach, and the best for showing a group, isn't to look at the Sun at all.
Pinhole projection: make a small hole in a piece of card, hold it in sunlight, and let the light fall on a second card held a metre or so behind. The spot of light is an image of the Sun, and during a partial eclipse you will see it as a crescent. It costs nothing.
Telescope projection: with a suitable instrument, project the eyepiece image onto white card held behind it. This shows sunspots clearly and lets several people watch at once. Not all telescopes tolerate it (the heat can damage some designs, particularly catadioptrics) so check before trying.
A natural version happens by itself: during a partial eclipse, gaps between leaves act as pinholes and scatter hundreds of small crescents across the ground beneath a tree. It's one of the more beautiful things about a partial eclipse and costs no equipment at all.
The one exception
During totality of a total solar eclipse (and only then) the Sun's disc is entirely covered and you can and should look directly with no filter. The corona can't be seen through eclipse glasses, which block essentially all of it.
The critical part is timing. Totality lasts a specific, known number of minutes at your location, and the moment the first sliver of photosphere returns (the diamond ring) filters must go back on immediately.
Know your local timings to the second before the day, and if you're unsure, wear the glasses. No view justifies the risk of misjudging it.
This exception applies only to total eclipses. During an annular eclipse a ring of the Sun's surface remains visible throughout, and filters are required for the entire event.
Checking your eclipse glasses
- Look for the ISO 12312-2 marking, and buy from a reputable supplier, counterfeits with the marking printed on them have circulated.
- Inspect for scratches, pinholes or separation from the frame before every use. Discard anything damaged.
- Test indoors first. Through safe glasses you should see essentially nothing except very bright lights. A domestic bulb should be barely visible at most.
- Supervise children continuously. Glasses slip, and a child will not report a problem they can't feel.
- Don't use them with any optical instrument. Eclipse glasses in front of your eyes plus binoculars in front of those concentrates light onto the film and can burn straight through it.
Still wondering
- Can you damage your eyes looking at the Sun?
- Yes. Solar retinopathy damages the retina and is painless, with symptoms typically appearing hours later as a blurred or dark patch in central vision. It can be permanent, and cases rise after every widely publicised eclipse.
- Are sunglasses safe for viewing an eclipse?
- No, even stacked. Only filters certified to ISO 12312-2 are safe for direct naked-eye viewing. Exposed film, CDs, smoked glass and welding glass below shade 14 are also unsafe because they don't reliably block infrared.
- When can you look at a solar eclipse without a filter?
- Only during totality of a total solar eclipse, when the Sun's disc is completely covered. Filters must be replaced the instant the first sliver of the Sun's surface reappears. During an annular eclipse, filters are required throughout.
- What is the safest way to watch a partial eclipse?
- Projection. A pinhole in card projecting onto a second card shows the Sun's crescent shape with no risk at all, and works for a group. Gaps between leaves do the same thing naturally, scattering crescents across the ground.
Natalie Hasselbank