Yes.

What do you think this is?

I would imagine some people would think it's some kind of game or maize or like a game of go or something.

It does look like it.

Didn't it?

Would it help if I told you that the little hexagons, some of them were made out of plastic and someone were made out of lead people who know who you are going to assume this has something to do with astronomy?

It does, in fact, the leads a bit of a giveaway, because one of the things that people everyone knows about lead is that X rays don't get through lead.

And in fact, this is part of an X ray telescope.

It's sort of the equivalent of the lens in an X ray telescope.

So the bit that goes at the top so it's the bit that the X rays first passed through before they get to the detective in X ray telescope tense.

It doesn't have to be a closed, too, but basically you've got this thing kind of up there somewhere.

And then you guys got a detector down here that just detects the X rays that goes over the whole of the front.

Yes, it is.

I mean, it's kind of the equivalent of a lens, but this comes back to how you actually make pictures with X rays.

This is a thing called a coded mosque on.

It's used on hard X ray and gamma ray telescopes.

It's actually used in medical imaging in other areas as well, but in the astronomical community, we put them on telescopes.

They tend to be the kind of telescopes that work at wavelengths that don't get through the atmosphere so they tend to be on satellites.

So, for example, the integral satellite, which is a gamma ray observatory on Easter Mission up there at the moment, has coded mosque on the front of it.

And so either you put them in space or the alternative is gamma rays get a least a little bit weighing down into the atmosphere.

So if you have a balloon, you you cannot have a balloon borne experiment with one of these telescopes on as well.

So I borrowed this from a friend of mine, a guy called Tony Bird Works at the University of Southampton.

So this is actually the University of Southampton coded mosque on.

He's an old mate.

Sorry.

Lent it to me for a week or so.

It does have a super treat, actually has this sort of strange rotational symmetry that actually, if you rotate the thing around, you get back to the same pattern you started with.

This isn't it really isn't the random pattern.

The pattern of effectively holds the bits that the X rays can get through, and the blocked out bits is carefully chosen.

This is a thing called a hexagonal, uniformly redundant array, or ahora its technical name for it.

But it's actually designed with with a specific objective in mind, and I put down clear weighs a ton way Need to back up a little bit and talk about how how you make pictures by City Hall Telescopes works how cameras work.

Normal optical wavelengths actually across a lot of the electromagnetic spectrum.

The where camera works is the way your video camera works that you got a lens at the front, which focuses the light down onto a detector at the back.

Typically a CCD these days, which records the light that's come from us.

So essentially you're taking all the light from came from a particular direction and you're focusing it down to a particular point on the detector, and that works fine.

But optical wavelengths, because it relies on the fact that you've got things like lenses or mirrors that allow you to bend the path of light so you can focus, like down in this way X rays, at least that the soft X ray and the things you can still actually focus, like you have to start getting a little clever because if you just put a mirror in the way of an X ray, just go straight through you put a mirror to very oblique angle.

The light will still get reflected off it, so you can still focus, like even at X rays.

You can do it with the same material.

If you have the same material viewed face on X rays, just go straight through.

If you think about that, atoms within it as the little balls, then if you think about it when its face on, there are gaps between the balls.

But if you take the same thing and view it very close to a John now, there are no longer any gaps on so actually the X rays, which penetrated perfectly easily when it was face on when it said the bleak incidents will deflect off the surface and so you can still focus.

Now it's It's quite hard to do, because if you think about it, you've got a given area of your mirror.

If you then put it in angle like that, you suddenly only have a very tiny area.

So to build an X ray telescope this way, they actually build these nests of mirrors inside each other, each of which sort of deflects a little bit of light so you could end up forming him an image that way.

But even that breaks down with the time you get to the heart X ray end and the gamma ray end of things.

Nothing you can do will focus the light effectively, so you need some new technique for imaging.

And that's what this is is.

This is a thing called said.

It's a thing called a coded mask, and essentially all it does is it throws a shadow.

If this were the telescope, supposing there was only one source out there, one bright quasar.

Massive black hole meeting loads of X rays and you wanted to know where it was in the sky.

All you have to do is point this telescope somewhere in vaguely the right direction.

And then the X rays from that quasar will come through the mosque here.

And you know where they hit the lead?

They be stopped where they hit the plastic.

They just go straight through on DSO.

You've now got your detective behind which records the X rays.

It'll just see a picture essentially off this mosque.

But where that mask appears on the detector will tell you what direction the light was coming from, just like if you were looking.

If you're looking at shadows, normally you can tell where the sun is in the sky, just from the pattern of shadows.

So this is doing exactly the same thing from the pattern of shadows that this mask casts on your detector, you can tell where that source was, So couldn't you just make that a big X or a straight line?

Was it was this funky, groovy pattern that it is.

So that's because there is more than one source out there, so if there were only one source.

You you have a strong, very dull.

But actually almost any pattern will work because you could just see the pattern of shadows.

What's clever about this is that actually, even if you have multiple sources, it can still produce it, tell you where they all are and how bright they are.

So I'm gonna guess give you a demonstration of how these things work with a nice little optical.

Models are actually have made one of these coded malsky.

This is actually the same design as the one on the integral satellite up there in space at the moment.

But we're over the making out of blocks of tungsten or lead.

I've made it our transparency sheet in the photocopier.

Here's my high tech camera X ray telescope made out of an old cardboard box and there's the coded mask that goes in the top.

And obviously, then the detective will be down here at the bottom, and so we could very easily see what happens and shine it through.

You can see basically you get just the shadows of the of the mosque and when the lights in different places, obviously the pattern moves around.

So by recording where the pattern is you essentially nowhere, the light source was.

So the clever part is that this is a trivial thing to do because actually, there's only one source out there.

It's pretty easy to figure out what the pattern is.

The neat part is, if there's more than one source, as we find astronomically and you want actually look at more than one thing at once, we can still do it.

So I need to borrow your phone for this.

So now if there was more than one source out there in space, so you can see what happens is you get overlapping shadows so you can see in some places you have white.

In some places, you have black.

In a lot of places, you have shades of gray, just depending on exactly how things line up.

Depending on where the sources are, you end up with these different overlapping patterns.

Okay, okay, policy fountains, and it's just a It's a pretty simple, simple job to figure out what's doing.

The clever part about these, whether it's uniformly, were done in their ways, whether it's one like this, which is exactly whether wants one like this, which is designed around squares.

The clever thing about them is that that pattern of blacks, whites and grays you can use to interpret whatever is going on in the sky.

There's never any ambiguity.

So, in fact that if you like, there's a unique way you can go from the things you detect that patterns of shades of gray that you detect on your detective plane.

You can go all the way back to saying exactly what the sky must have.

Bean.

So there's no degeneracy.

There's no confusion.

There's no possible multiple combinations of things that could produce the same patterns of shades of gray.

There's a eunuch unique way to go from what you actually detect here, very simply, back to what an image of the sky looks like.

Does that mean?

Designing these things is bit of an art form in the mathematical sense of the word, it is indeed an art form, so there's a there's a rather clever mathematical algorithm, allows you to just divine one of these optimal raise that really has no ambiguity at all between what you detected.

What the sky was doing on the second question is, why aren't they all the same?

Surely, once you've got a pattern that does that job, they must just have the exact same pattern on them.

So, in fact, quite a lot of them do have the same patterns on them.

But this, for example, different sizes.

But, Ray, you might want in terms off what resolution of images you're trying to make.

What size of field of you you're trying to make me, Really.

But let me show you a picture of a very pretty picture.

So here's a whole series of these hexagonal uniformity, redundant arrays, and you could see a different order.

So basically, they're making smaller and smaller little blocks, which allows you to make finer and finer detailed pictures on.

Actually, the thing that strikes me about them is they're really rather beautiful.

Special is the quality of that mirror.

That mirror was engineered to be so perfectly optically smooth that if you took this 2.4 meter diameter mirror, scaled it up to the radius of the earth.