Nearly the whole Sun will disappear over Putney on Wednesday evening.
A solar eclipse happens when the Moon passes directly between the Earth and the Sun, blocking some of its light. On Wednesday, the Moon starts creeping across the Sun just after 6:17pm, reaching its deepest point at around 7:12pm, when close to 90 per cent of the Sun will be covered as seen from London. It’s finished by 8:06pm.
The Moon lines up precisely enough to block the Sun completely only for people standing in a narrow strip of the Earth’s surface, called the path of totality. On Wednesday, that path runs over Greenland, Iceland and northern Spain, not the UK. London sits well outside it, which is why this is a deep partial eclipse here rather than a full one. It still counts as the deepest the UK has seen since the total eclipse of 1999, and there won’t be one this good again until 2081. A full total eclipse from Britain is not due until 2090.
The whole thing fits into under two hours because of how the Moon moves. It’s actually travelling at around 2,300mph, but because it’s so far away, it only appears to creep sideways by about its own width in the sky each hour. The Sun and Moon look almost exactly the same size to us, so the Moon only has to slide a little more than one of those widths across the Sun to cover it and clear it again.
Don’t expect it to go properly dark, even at 90 per cent. What you’ll actually notice is the light thinning and cooling, more like a heavily overcast afternoon or dusk arriving early than night. Scientists who study eclipses have measured air temperature drop by around 1.5°C at this level of coverage, and once the Sun passes about three-quarters covered, birds and other animals reliably start reacting: birdsong tends to quieten, some insects become less active, and you may notice gulls or pigeons heading somewhere to roost earlier than usual.
Putney’s eclipse, minute by minute
Drag the slider or press play to run Wednesday evening. The coverage figure is computed from the real disc geometry; times, coverage and the Sun’s height are sourced (Royal Observatory Greenwich; tutiempo.net ephemeris for London).
Where to watch it
The Sun will be low in the west-northwest the whole time, only around 10 degrees above the horizon at maximum. That’s about the width of a closed fist held at arm’s length against the sky, so not far up at all: any building, hedge or tree line of that height in the right direction will hide it. Royal Observatory Greenwich’s advice is to find any high, open spot with a clear view in that direction. That’s the real test for a local spot, not just whether the forecast looks sunny.
Putney Heath, Wandsworth Common and Wandsworth Park are all worth trying if you’re near. Your own street or a friend’s upper floor with a west-facing window may work just as well. Check what’s between you and the sunset before 6pm. Even a dedicated observatory isn’t immune to this problem: Hampstead Scientific Society’s own site won’t be opening for the eclipse at all, because the Sun will be behind trees there on the day.
How to watch it safely
Never look directly at the Sun during this, even though most of it is covered. The sliver that’s left is still intense enough to burn the retina, and because the retina has no pain receptors, the damage doesn’t hurt while it’s happening. Symptoms like blurred vision or a blind spot can take hours to show up, by which point it’s done.
Regular sunglasses, however dark, don’t fix this. They cut visible light by maybe 10 to 20 per cent and do almost nothing to the invisible ultraviolet and infrared light that causes the damage. Proper eclipse glasses look similar in shape but use a much darker filter, usually a silvery or black film in cardboard or plastic frames, that cuts sunlight by a factor of roughly 100,000. Put a genuine pair on indoors and you shouldn’t be able to see ordinary household objects through them at all.
They’re certified to a standard called ISO 12312-2, which should be printed on the glasses themselves, and a genuine pair usually costs just a few pounds. The catch, this close to Wednesday, is timing. Several UK astronomy retailers, including First Light Optics, have now sold out online, and even Amazon’s fastest delivery on ISO-certified glasses lands the day after the eclipse. If you want a pair for Wednesday, a specialist camera or astronomy shop that keeps walk-in stock is your best realistic option, phone ahead before you travel, or ask around locally for someone who already has a pair, checking it for scratches, punctures or a lifting film before you use it. Ordering online today is unlikely to get glasses to you in time.
No glasses, and can’t get any before Wednesday? Here’s what’s actually realistic instead:
- A pinhole projector made from a sheet of paper
- An ordinary kitchen colander, held so the Sun’s light falls through it
- The dappled shadow cast by tree leaves onto the pavement
All three project a small crescent of light onto a surface. You’re looking down at a piece of paper or the pavement, not up at the sky, and it’s genuinely a modest, five-minute science trick rather than a dramatic view of the Sun itself. Worth doing, especially with kids, but don’t expect it to carry the evening.
The bigger reason to go outside on Wednesday needs no equipment at all. The light thinning, the temperature dip, birds and other animals reacting as though dusk arrived early: none of that requires glasses, a colander or anything else, just being outside and paying attention between about 6:15pm and 8pm. And if you want to see the Sun’s shape directly but can’t get glasses in time, the Royal Observatory Greenwich is running a free livestream and a free in-person event from 4pm, with its own solar-filtered telescopes, so you don’t need to own a pair of glasses at all to get a proper look.
Will you actually see it?
Today’s Met Office forecast has Wednesday fine, dry and sunny for London, with the current spell of heat peaking on Wednesday and Thursday. That’s about as good a starting forecast as an eclipse gets, though it’s a forecast, not a promise, and it can still shift before Wednesday evening.
A generally sunny day and a clear western horizon at low level aren’t quite the same thing, either. Last year’s Blood Moon taught plenty of Putney stargazers that clear forecasts don’t always deliver: cloud rolled in over Putney that night and blotted most of it out, forecast or no forecast. Have a backup spot in mind, just in case the one you’d planned on has a cloud bank sitting over the river at the wrong moment.
If you’re still out once the eclipse has finished, don’t head straight in. The Perseid meteor shower, one of the best of the year, peaks that same night, and because the Moon will be new (it’s the thing doing the eclipsing), there’ll be no moonlight to wash the meteors out. The best rates come after midnight, so it’s worth staying up if you can manage it.
And if cloud gets in the way of either event, there’s a second chance a fortnight later: a 90 per cent partial lunar eclipse is visible from the UK in the early hours of Friday 28 August.
Did you catch it? Send us your photos, taken through a proper solar filter, and we’ll share the best.
