A public event, organised by an astronomical society, is probably the safest and most enjoyable way to watch the eclipse. Image credit: Stuart Atkinson

Mar 17, 2015 Getting ready for the March 20th solar eclipse

Sen—Wherever you are in the world as you read this, if you stop for a moment, open the window and listen very carefully, you can probably hear the sound of frantic clicking coming from the direction of Europe, as countless thousands of amateur astronomers and skywatchers repeatedly check their favourite weather websites for updated local weather forecasts for Friday morning.

Why? Because on the morning of Friday March 20th a solar eclipse will be visible across much of Europe, and time is ticking…

If you’re not usually interested in astronomy and don’t know the science behind what’s happening, it’s pretty simple: basically, the Sun, Earth and Moon are all lining up on that morning, with the Moon in the middle. The Moon will cast a shadow on the Earth, and people in that shadow will see the Moon covering all or part of the Sun, depending on exactly where they are. Contrary to what many tin foil hat-wearing nutters on the internet would have you believe, this happens fairly often and won’t cause any problems. Much to the disappointment of the same dribbling conspiracy theory-loving fruit loops who oh so confidently predicted the Mayan Apocalypse in 2012, and the destruction of Earth by Comet ISON a couple of years ago, there’ll be no earthquakes, tornadoes, magnetic storms or anything like that.

From a very, VERY small area in the very centre of that shadow—basically the Faroe Islands and swathes of the storm-tossed ocean on either side of them—the eclipse will be total. The Moon will cover the Sun completely, reducing it to a black hole in the sky surrounded by a ridiculously-beautiful feathered halo of silvery blue light. This doesn’t happen very often, and consequently, even as you read this post, parties of dedicated eclipse-chasers, laden down with small fortunes worth of cameras, telescopes and equipment are heading for those remote islands in planes and on ships, like Indiana Jones in pursuit of a precious artefact. By Thursday the Faroes will be swarming with wide-eyed, jet-lagged eclipse junkies, desperate to see the Moon cover the Sun, again, or for the first time. I’m actually worried the Faroes will tip up and slide into the sea under the weight of all the eclipse tourists, but we’ll keep our fingers crossed…

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Image credit: F Espenak NASA

As you can see from this excellent chart, produced by the always-excellent eclipse expert Fred Espenak, for everyone else across Europe, further eastwards and down into Africa, the eclipse will just be a partial one, with the Moon only covering part of the Sun. (Sorry, readers from the US or southern hemisphere, this time you won’t see anything, it’s a northern hemisphere only show.) Exactly how much of the Sun will be covered for an observer depends on where they’re looking at it from – the closer to the Faroes and the track of totality they are, the more of the Sun will be obscured by the Moon for them. But across the whole of the eclipse area people are preparing for the Big Day.

“Eclipse fever” is certainly growing here in the UK, and with just a few days to go, despite poor weather forecasts excitement is really building up. Astronomical societies like mine are finalising their plans for public eclipse watching events; schools are mass-producing pinhole eclipse viewers; last-minute holidays off work are being booked by people eager to see one of Nature’s greatest shows.

But as exciting as this eclipse is, it’s important to remember that anyone wanting to watch it will have to be very, very careful. From my home in Kendal, in England’s beautiful Lake District, around 90% of the Sun will be covered, and people north of me will see even more. But with even a small part of the Sun left visible, watching the eclipse will require great care and special equipment.

Now, common sense alone should be enough to tell you that if even a small part of the Sun is left visible it will be far, far too bright to look at with just your naked eye, just as it’s dangerous – and let’s be honest, pretty stupid – to look directly at the Sun when there’s no eclipse on. The Sun is, if you needed reminding, brilliantly, blindingly bright, and if you stare at the partially eclipsed Sun on March 20th without special equipment and techniques you WILL damage your eyes, it’s as simple as that. And if you were stupid enough to try to look at the partially eclipsed Sun directly through binoculars or a telescope, well, you’ll poach your eyes inside your skull. I’m sure no-one reading this would do something like that. Right?

So how DO you watch this incredible event safely? Well, the good news is there are lots of ways to watch it without risking your eyesight, but before we look at them let’s quickly go through all the ways NOT to watch the eclipse, because there are a lot of frankly terrifyingly stupid “hints and tips” doing the rounds. 

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Image credit: S Atkinson

First of all, no matter how dark or cool-looking yours are, or how much they cost, SUNGLASSES will be no use at all for watching the eclipse. Even the darkest of dark shades from the MATRIX films are nowhere NEAR dark enough to watch a solar eclipse through. You need something which will make the Sun so faint that you won’t be able to see *anything* else around you, and obviously that’s not what sunglasses do.

Amazingly, SMOKED GLASS is still being suggested by some people as a safe way of looking at the eclipsed Sun, but it’s absolutely not. It’s true that if you hold a piece of glass over a flame you will get a very dark, sooty coating on it, which might be dark enough to see the Sun through, but it’s just not safe, because even the lightest touch against the sooty stuff will remove it from the glass. So, although grainy sepia-toned photographs show that smoked glass was the method of choice for stern-looking eclipse watchers back in Ye Olden Times, please don’t even think about it in this space age, Apple era. We can do a lot better than that now.

A few other things you can’t use for watching the eclipse: coloured foil sweet wrappers; a CD or DVD; the tin foil tea bags are packaged in; baking foil; cinema 3D glasses. Honestly, I’m not making those up. People are actually suggesting those as ways of watching the eclipse, which isn’t just ridiculous it’s dangerous too. 

No. Essentially there are only two ways of watching the eclipse – directly, or by projection.

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Image credit:  S Atkinson

Directly

If you want to look directly at the Sun during the eclipse you will need to reduce its brightness or you will damage your eyes. Please, if you’re in any doubt, read that again – you WILL damage your eyes. How do you do that?

Well, you will need something which cuts down the Sun’s light, and there are several different materials and products you can use.

ECLIPSE GLASSES (or “eclipse shades” as they’re sometimes called in adverts) are a safe and sensible way of watching a solar eclipse. They might look like they’re just cheap cardboard things with coloured plastic for lenses, but that’s not true. Ok, the cardboard bit is true, but the lenses are made of a very special material which reduces the Sun’s brightness to a tiny, tiny fraction of what it usually is, allowing you to look at it directly. Eclipse glasses reduce the Sun to a disc surrounded by total blackness, they’re so dense. Depending on which type of material their lenses are made from they can make the Sun look green, orange or blue, but the colour really doesn’t really matter. All that matters is that they make the Sun safe to look at.

If you want a pair to use during the eclipse your local camera or telescope shop might have some, but there are lots of suppliers online, just do a Google search for “eclipse glasses” or “eclipse shades”. When you get your pair, check carefully that there are no tiny holes in them by holding them up to a light bulb, or the sky. If you spot any pinprick holes are in the lenses, don’t use them; send them right back. And promise me that if you drop and graze/puncture your glasses on the day of the eclipse you’ll stop using them right away? Ok.

Oh, and please, please, do NOT put on a pair of eclipse glasses and then look into a telescope or binoculars. They will melt and bubble away in moments in the heat of the concentrated sunlight and you will damage your eyes.

What else can you use if you can’t get hold of eclipse glasses in time? Well, you can sometimes buy individual plates or pieces of welding glass from hardware shops or places that sell material for the building industry, and you can use those as solar filters by holding them up to the Sun. They have to be really dense though, strength/grade 14 or more. Through them you’ll see the Sun looking like a green disc, and will have a great view of the eclipse. Just use them for brief glimpses though, don’t stare at the Sun through them for long periods.

There’s one more way of looking right at the Sun during the eclipse—by looking at it through a telescope that has a special solar filter fitted over the front. Many amateur astronomers will be using these on the day, but they’re not something you want to even think about unless you’re an experienced solar observer and know exactly what you’re doing.

The easiest (and cheapest!) way to watch the eclipse will be by using…

Projection 

It will be possible to watch the eclipse by projecting an image of the Sun onto a makeshift screen. But what do you use to do that? Experienced amateur astronomers will be using their binoculars and telescopes to project images of the eclipse onto screens and pieces of card, but again, unless you know what you’re doing you shouldn’t even think about trying to do that.

Thankfully you don’t need binoculars or a telescope to project the Sun during the eclipse. All you need are two pieces of card and a pin to make a very basic but effective “pinhole projector”. Simply prick a hole in the centre of one piece of card, hold the other behind it and line them both up with the Sun. The hole will act like a tiny lens and project a small image of the Sun into the second card. How simple is that?

Using this “pinhole projection” method you will be able to view a (very) small image of the eclipsed Sun on a piece of card without any expensive or high tech equipment at all. It won’t be as impressive a view as you would get by using binoculars or a telescope, obviously, but you will be able to see the eclipse.

And if you can’t lay your hands on a couple of pieces of card and a pin, what do you do? Well, you might not know it but there’s probably an advanced solar eclipse viewer in your house already…

Go into your kitchen and look at your colander. See how it’s got dozens of little holes in it? Well, each of those holes can act as a pinhole projector, just like the hole in the piece of card described above, so if you hold your colander up to the Sun during the eclipse you will see lots of small images of the eclipsed Sun projected through its holes! Put a piece of white card behind it, or just a bare wall, and you will be able to watch the eclipse!

What? You don’t have a colander either? Oh, for pity’s sake… ok, if you’re that unprepared, Nature herself will help you out! If you go and stand next to a bush, or under a tree, dozens or even hundreds of shimmering images of the eclipsed Sun will be projected onto the ground around you or buildings next to you, through tiny gaps in the branches and rustling foliage.

So, you see, there are many ways to watch the eclipse on March 20th. You can either go high tech, and use a pair of eclipse shades, or a telescope, or binoculars, or you can go low tech, with a pin and pieces of card. You can even just be incredibly lazy and go and stand under a tree and let the tree do the work for you!

Time for some honesty, I think. Although many astronomers writing about this eclipse won’t admit it, the elephant in the room is that size really does matter—the size of the image of the Sun you’re looking at, I mean. So, although you can see the eclipse with just a pinhole projector, or a colander, you will only see a very small image of the Sun that way, and the eclipse won’t blow your head off. In fact you probably won’t see much until the event is well underway, and a good proportion of the Sun is obscured by the Moon. When the eclipse reaches its maximum even low-tech viewing methods should let you see the Sun reduced to a crescent, but when the eclipse throws itself into reverse the same will be true—looking at a small image you probably won’t be whooping and hollering with excitement, and might even wonder what all the fuss is about…

If, however, you can get your hands on a pair of “eclipse glasses”, or a piece of welding glass (remember, density #14 or more), then to be honest you will enjoy the eclipse a lot more, because you will be looking at a bigger image of the Sun, it’s as simple as that. To the appropriately-protected naked eye the eclipse will look fascinating from around ten or twenty minutes in. when there’s a very noticeable bite out of its side, and at maximum eclipse the Sun will look very striking indeed.

But in all honesty, despite all the hype and build-up, it has to be said that the people who will get the most out of the eclipse will be those who look at images of it projected through binoculars or telescopes, because they will be able to enjoy a really big and bright image of the eclipsed Sun. This is why I am so passionate about urging people who want to see the eclipse to check if their local astronomical society is holding an eclipse-watching event, with telescopes set up for projecting the Sun, like we did here in Kendal a few years ago...

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A public event, organised by an astronomical society, is probably the safest and most enjoyable way to watch the eclipse. Image credit: Stuart Atkinson

Amateur astronomy is now such a popular hobby that most towns and cities have at least one astronomical society. Large cities might even have several. If you’re not sure if there’s one where you live, try Googling for them, or ask in your local library, which should have a directory of local groups, clubs and organisations. If you then find that your local astronomical society isn’t holding an eclipse event, then they should be, and you should be contacting them and asking them why they’re not. In my opinion astronomical societies have an obligation and a duty to ensure people who want to watch the eclipse safely are able to do so. I would hate to hear that someone injured their eyes looking at the eclipse the wrong way because their local astronomical society couldn’t be bothered to hold an event. That would be a great shame.

And stories are now appearing in the press over here about schools actually banning their pupils from watching the eclipse outside, on health and safety grounds. Instead they’re going to show the kids the eclipse inside, on TV. What a shame, what a crying shame. I know they mean well, and have their pupils’ best interests at heart, but this eclipse offers those teachers, and all teachers, a golden opportunity to excite kids about science and the natural world, and with just a little bit of research work on Google they could have found some fantastic websites describing how to watch the eclipse safely. At the very least they should be contacting their local astronomical society and asking their advice, and taking the kids along to any eclipse-watching events they’re holding.

Of course, every eclipse watcher, wherever they are, will be totally at the mercy of the weather on Friday morning. Despite decades of being frustrated by the English weather, of missing one meteor shower, comet, auroral display and eclipse after another, I’m still an optimist, and am looking forward to setting up my telescope on Friday morning in glorious sunshine. But what if it’s cloudy?

Well, of course we’re all hoping for crystal clear blue skies on Friday morning, but realistically that’s not very likely. I’ve been checking the weather forecasts and it’s looking a bit… challenging, with up to 72% cloud cover for my part of the world. To be honest, I’d take that, because if it’s only partly cloudy I should still be able to see some of the eclipse, it will just mean waiting for gaps to drift over the Sun and grabbing views of it when I can. Which can actually be quite fun, believe it or not; despite what others may say or write about them, solar eclipses move very, very slowly, not much changes from minute to minute, so a little bit of cloud doesn’t have to be a bad thing, it can actually make watching the eclipse more exciting in a weird way as people grab any glimpse of the Sun they can get. You don’t have to be able to see the Sun for every single minute of the eclipse from start to finish.

But if it’s totally overcast where you are on Friday morning, what do you do? Well, if you have time for a Plan B can you jump in the car, or catch a bus, and find somewhere less cloudy. But if you don’t have that option, if you’re stuck at work during the eclipse and trying to watch it on your break, or can only sneak a look at it through the window as you work, or if you just can’t get transport to an alternative site, all you can do is look at the cloudy sky, shake your fist at it, hurl a few choice swear words at it, and feel angry all day, and even angrier that night when you watch the reports and see others’ beautiful photos on the TV news.

…unless you’re in an area where the Sun will be 90% eclipsed or more. Then, at the maximum of the eclipse it could get very dark, dramatically dark in fact. So even if you are somewhere so cloudy you can’t see the eclipse itself you should still be able to tell the eclipse is happening, up there behind the clouds.

So, that’s it, that’s what’s happening. If you can, get yourself along to an organised event and have a great time. Just think what it’s like on Bonfire Night – it’s much more enjoyable watching a fireworks display as part of a group, soaking up the excitement and reaction, than it is watching it on your own. If you can’t get along to an organised event, or if there isn’t one near you, then just do the best you can with what you’ve got to hand. But do try and watch it! Some killjoys who know nothing about science will try to tell you that there’s NO safe way to watch the eclipse, that the only safe way to watch it is on TV (and there will be a LOT of eclipse reporting on the TV on the day). That’s rubbish. Anyone can watch this exciting event safely, it just takes a bit of preparation and common sense, that’s all. Reading this article was enough to prepare you – the common sense part, well, that’s up to you.

Good luck!

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