BBC The Sky at Night (1957) s24e01 Episode Script
Light Fantastic
Welcome to Selsey.
This is where I have my home and my telescopes, including my beloved 12.
5 inch reflector.
In this special programme, we're going to look at 400 years of the telescope in astronomy.
It's a marvellous story and over the years, we've been to some of the world's great observatories.
100 years ago, the world's largest telescope was the great reflector set up by the Third Earl of Rosse at Birr Castle in Ireland.
The telescope was completed in 1845.
We're going to talk about it in this evening's Sky At Night.
I am standing on top of one of the most remarkable telescopes in the world.
We're at Kitt Peak in Arizona.
Mount Wilson is one of the peaks overlooking Los Angeles.
It's 5,700 feet high.
Nothing special.
And outwardly there's nothing to mark it out.
La Palma is now becoming famous in another direction.
It's here that one of the world's great observatories is being set up.
The great 28-inch telescope is coming home where it belongs at the Old Royal Observatory in Greenwich Park.
Sun-soaked palms and temperatures in the mid-80s, but there's another angle to Hawaii too.
A region of thin air, icy cold and winds up to 150 mph.
And that's where I am now.
On the top of Mauna Kea, nearly 1,400 feet above sea level.
Its great strength lay in its light-gathering power which was greater than any other telescope until that time.
In astronomy you want to see very faint things.
To see faint things you need as much light as you can get.
The bigger the mirror, the more light you can collect.
This is where the big Rosse mirror came in.
Even with the naked eye, you can carry out a great deal of work in astronomy.
But of course, the telescope makes all the difference.
So who made the first telescopes and who first turned them skyward? Most people say Galileo.
Well, I talked to one of our regular guests, Dr Allan Chapman, who has other ideas.
All that we can say is on the 2nd October, 1608 a German living in Holland, in Middelburg called Hans Lipperhey presented a petition to the state's general, the Dutch government, for a device that made distant objects appear close using a pair of lenses.
The thing is he didn't get his petition or his claim, because two other Dutchmen immediately leapt in and said, "We've got the device too", so actually we don't know.
The key thing is though, what happens is this is the first use of the telescope in the world.
Now because he didn't get a patent claim, very quickly these devices went on sale across Europe.
They were on sale in Frankfurt, Paris and various other places by the end of 1608.
Now an Englishman called Thomas Harriot acquired one from somewhere.
He called it his "Dutch trunk" and what the original device was was a pair of lenses in a tube.
An object glass and an eyepiece.
The object glass has to be thicker on both sides.
It has to be convex.
They eye piece has to be narrower in the middle - a concave.
Put them both in the right positions and "boom!" - suddenly distant objects are very close.
Now what the Dutch were using it for was to look at ships or distant buildings.
The Dutch of course at that time were in a war of liberation against Spain.
Useful strategic device.
But Harriot uses them scientifically.
On the 26th July, 1609, he looked at the five-day moon.
So Harriot was the first telescopic astronomer.
Without any doubt.
Or the first one on written record.
What his telescope looked like was something like this.
I made this replica which is the same as the two lenses object glass at this end, eyepiece there.
And this magnifies about 20 times.
When I look at the moon with this, I can see the main craters.
One or two known points but certainly the Mare Nectaris the Mare Tranquillitatis on one or two features.
And then all of a sudden the realisation is the telescope shows you things you can't see without it.
And over the course of about a year and half, Harriot makes a series of maps.
Now it's true by the summer of 1610, he would have had Galileo's observations, which had been published in Venice in March 1610 and on sale in England in June of that year, but also too, Harriot is making better drawings of the moon than anything in Galileo, and then he makes an undated map, but certainly around 1610-11, of the whole moon.
And that is a stunningly beautiful map.
It is.
It has the seas, it has lots of prominent craters.
He had no idea what he was looking at.
He didn't quite know what the whole moon was made of, but as a piece of cartography, it was superb.
These early telescopes were refractors then we come to reflectors.
And this little telescope, this brass instrument on loan from the Science Museum is of the Gregorian pattern.
This is how a Gregorian worked.
Very kindly, the Science Museum has provided us with a cutaway instrument.
As these are nearly 200 years old, we handle them with white gloves so acids from our fingers won't affect the metal.
You have a parabolic mirror down here.
The light comes in, hits that mirror is reflected back up to a second mirror it's then reflected back down through a hole in the main mirror and to an eyepiece.
Once you've got the reflecting system you are able to see bigger, brighter images.
because it was easier to make big mirrors than big lenses.
What William Herschel called space penetrating power.
They realised very early on when you make a more powerful telescope, you see more stars, more stars, more stars.
Is the universe infinite? Does it go on forever? The telescope is the first instrument that shows us we can see things beyond our five senses.
And we think the telescope, the microscope, the barometer In more recent times, photography, digital imagery, TV.
I suggest the telescope is the first that shows us we can go beyond normal vision.
In that respect, it's transformative in so many ways.
This is my main telescope, my 15-inch reflector.
Well, here at Selsey, conditions are as good as they are anywhere in England, but of course, they're not perfect and the world's big observatories have to be very carefully sited.
One of these is Kitt Peak in Arizona, and Chris went there.
Deep in the Arizona desert, 40 miles away from the bright lights of Tucson, is a world-famous collection of telescopes.
Astronomers first came here more than 50 years ago for the clear skies and the dry air.
From a distance, you can still see the sparkle of the silver and white domes, gleaming in the relentless sunshine.
Welcome to Kitt Peak, America's national observatory.
With 25 or so domes scattered across the mountain top, this is the largest collection of professional telescopes anywhere on the planet.
The largest of the more than 25 telescopes here can be used by astronomers from any university or any country.
This is the home of Astronomy for All.
Down in Tucson is the National Optical Astronomical Observatory, which is in charge of Kitt Peak.
It shares a campus with the University of Arizona, and as students walk to class, I talk to Doug Isbell about the early days on Kitt Peak.
So how long have there been telescopes on Kitt Peak? Well, it was 50 years ago that Kitt Peak was elected as the site of the US National Observatory after a search across the continent.
About 150 sites were looked at, and Kitt Peak was selected due to its very clear, dry weather, its overall good climate, its dark skies and also it was close to practical things like a university, and an airport where the scientists could fly in from their universities, which were largely in the East.
It was founded to give Eastern and mid-Western scientists a place to do astronomy with dark skies.
So what was on the mountain before the astronomers arrived? We're on the land of the Native American Tohono O'odham Nation, separate from the United States in many respects, and we're a tenant there.
We're honoured to be on their land.
We have a long-term lease through the National Science Foundation with the Tohono O'odham Nation.
On the mountain, the telescopes are being prepared for the night.
In charge of the oldest large telescope on the mountain, the 2.
1 metre, is Dr Howard Bond.
When the telescope was new, he would've been assisted by an operator, but now he has to do everything himself.
Times have changed! It was with this telescope that astronomers were first able to probe the fingerprints of hydrogen in distant galaxies, helping them piece together the history of the universe.
Today, Howard is using the telescope to follow up on observations made using the Hubble Space Telescope.
Tonight, we're working on a programme that's related to the Hubble Space Telescope.
So with Hubble, we're measuring the distances to stars using the parallax effect.
Those measurements are relative to surrounding background stars, and to get an absolute true distance, we need to make an estimate of how far away those background stars are.
To do that we measure their brightnesses and colours, which is a perfect thing for a ground-based telescope, like the 2.
1-metre telescope that you see behind you.
These are relatively local, it's surprising we don't know the distance well already.
Why do we need to know so accurately how far away these stars are? The problem is we use these Cepheid variable stars, very bright stars and we know the brightness depends on the period of variation.
The question is setting the zero point.
There aren't any Cepheids that are close enough to the earth to have their parallaxes measured accurately with ground-based telescopes.
The nearest Cepheid variable is the North Star, Polaris, which I'll be observing tonight if the weather stays clear.
Hasn't Polaris been behaving oddly recently? Yes, its range of brightness has been going down.
Some people predicted it would stop being a variable star.
It's bottomed out and it's still varying at a low level.
Is this your first night on the telescope? This is my third night - no, it's my fourth! I've already had three.
So you've been living nocturnally? Trying to, yes.
If the skies stay clear, Howard will look at about 24 stars tonight to measure their brightness.
But this isn't the only telescope which will be working tonight.
This is the Mayall telescope, when it was built, the second largest optical telescope anywhere in the world, and still the largest on Kitt Peak.
Its giant, 4-metre mirror is used for everything from looking at the edge of the solar system to studying distant galaxies.
The designers of the Mayall telescope in the 1960s gave it a radical look.
The dome sits 92 feet above the ground in an attempt to keep it clear of turbulent air.
As with all telescopes, it's kept up to date with new cameras and instruments, but the control room still has something of the feel of the inside of a battleship.
Tonight, Dr Kimberly Herrmann is preparing to take a close look at some nearby galaxies.
When we look at spiral galaxies, the rotation curves gives us the total mass of the spiral galaxy, but how much of that mass is in the bulge, is in the disk and is in the dark matter halo, that's what we want to know.
By studying planetary nebulae, we can look at the motions in and out of the plane of the galaxy to determine the disk mass in the galaxy.
Why are we interested in the outer regions? There are some very strange things going on in the outer regions.
There seems to be more mass out there than we would expect.
I'm trying to see how much light is out there.
If there's enough light out there to explain the mass I'm finding.
Kitt Peak was born from a noble vision - that good ideas win you time on telescopes.
It was and is astronomy for all.
These historical telescopes may not often grab the headlines today.
They serve as work horses rather than show ponies, but it's the meticulous work done here, night after night, decade after decade, that slowly reveals what our universe is like.
Kitt Peak remains in the forefront.
There are other great telescopes too, those in Hawaii or the Atacama desert.
All of these were built in the latter half of the 20th century.
It's an impressive instrument.
As with most large reflectors, the tube is a skeleton, and the mounting is a massive horse shoe.
The main mirror is 154 inches in diameter, or 3.
9 metres if you prefer metric, and that puts it in the world's top six.
When the question of an observatory on the top of Mauna Kea was first discussed, I'm sure there must have been plenty of raised eyebrows.
The difficulties were obvious - inaccessibility and above all, the effects of altitude on the observers, but the challenge was taken up and it's an unqualified success.
When you're building a big telescope, I suppose about 50% of the problems are engineering and the other 50% are optical.
Obviously, the main component optically is the big mirror of the telescope.
This rather strange-looking construction is the aluminizing chamber, inside which the mirror is kept until it's ready to be put into the telescope.
This has been brought out for us.
We're some of the first people to see it like this.
When I began the Sky At Night series in 1957, the biggest telescope in the world with the 200 inch at Mount Palomar in California.
But of course the early 20th century was the period of the first great reflectors and great observatories.
With me, Professor Richard Ellis of Oxford.
Welcome back to the programme.
Thank you.
A great period, wasn't it? A fantastic century of discovery in astronomy.
The large telescopes are, without question, contributed an enormous amount.
They've really shaped our view of the universe.
If one imagines the expansion of the universe discovered with the 100 inch Telescope and understanding Stellar Evolution with the 200 inch.
And now the Keck and European large telescopes pushing the frontiers to the most distant galaxies that we can see.
There are have been various telescopes that have marked new developments.
One of these was the 100 inch at Mount Wilson.
Tor a long time, the most powerful in the world and in a class of its own.
Yes, from the period in the early '20s until after the Second World War, the 100 inch was the largest telescope in the world.
Probably its biggest discovery was the expansion of the universe.
By Hubble, of course.
By Edwin Hubble himself.
There were early work that showed galaxies were moving away from us but Hubble showed the distance to a galaxy is correlated with the speed with which it's moving away from us.
He had to use the 100 inch for that, no other telescope could do it.
That' right.
This means the universe had a beginning.
That really is a profound discovery.
Perhaps the most significant discovery of the 20th century.
Hale masterminded the 100 inch.
He wasn't satisfied.
He was an amazing man.
He founded Cal Tech and the American Astronomical Society.
He was a relentless raiser of money for large telescopes.
There were many problems faced, both financial and technical.
The 200 inch was an amazing challenge.
Making the mirror was the biggest challenge of all.
There were several attempts to cast the mirror.
In the end, they were successful.
And that mirror is still in use celebrating 60th anniversary of world-beating science this year.
It is still in use doing frontier work.
It's a good example of how a telescope is a lasting achievement.
Telescopes are not stagnant things.
They can be updated with new instruments, and the 200 inch is testimony to that.
What do you think are the major advances by British technology? Firstly the Anglo-Australian telescope.
A fantastic project.
3.
9 metre telescope in Coonabarabran, Australia.
Its probably biggest achievement was the Galaxy Redshift Survey.
The so-called 2-degree field Redshift survey.
That was a huge step forward in our understanding of how much mass there is in the universe, the nature of dark matter, and the distribution of galaxies of various kinds, spirals, ellipticals on large scales.
The William Herschel telescope is on a better site.
It's a magnificent technical achievement.
It has fantastic instruments, including faint object spectrographs which were able to look at gravitationally lensed galaxies.
This was an era when Hubble was launched and so there was a good synergy between the Herschel telescope and the Hubble space telescope.
I'm a big fan of UKIRT, a very cost-effective telescope, very cheap, on the summit of Mauna Kea which is now doing a big infra-red sky search but it has achieved a lot in infra-red astronomy.
I would argue British astronomy and the infra-red was in the world lead for a long period when UKIRT was the largest infra-red telescope in the world.
Coming on to the VLT, how involved are we in that? Britain is a full member of the European southern observatory for many years now and most British astronomers are doing their cutting edge work on the ESO VLT.
This is 4 eight-metre telescopes, tremendous versatility, some of the best instruments in the world, particularly for spectroscopy and the infra-red and in the optical region.
What are the greatest achievements of the Keck, do you think? Firstly, the discovery of the most distant galaxies, up to Redshift 7 and beyond.
where we're looking back, 90-95% way back to the Big Bang.
That's really one area where I think Keck has been supremely successful simply because it's got fast spectrographs and 10-metre aperture.
Then I would select gamma ray bursts, energetic explosions We didn't know whether they were, oh heaven forbid, we didn't even know if they were in the solar system, milky way or distant universe.
They're not! They're a long way away.
And so these are tremendously energetic bursts of activity when two black holes or a black hole and a neutron star merge.
Finally the accelerating universe, the use of supernovae as standard candles to trace the history of the expansion.
Are you happy about that? I'm involved, Patrick so yes.
I'm very excited and it's a remarkable result.
It was found independently by two teams.
So the expansion is accelerating.
The expansion is accelerating.
Why? We don't know why.
We give a label of Dark Energy to it but who knows what that means? There's a lot of enthusiasm now in the astronomy community to get to the bottom of this.
There's a good achievement from the Keck telescope.
We said for a long time the Rosse telescope was superb, then the 100 inch, then the 200 inch.
Would you now say the Keck telescope is ahead of any other? It's hard to say.
The Subaru 8-metre telescope and the ESO VL in the Gemini observatories all of them are doing frontier work.
Keck has a wonderful advantage by being slightly larger.
10 metres over 8 metres does matter.
It does.
It's 10 squared over 8 squared.
Of course, Keck has a head start because it was on the scene earlier.
Much of the early work was creamed off by the Keck telescope.
That gave California astronomers an advantage.
The essential part of the reflector is this main mirror.
Everything depends upon how good the mirror is.
Chris has been over in Arizona seeing how 21st-century mirrors are made.
Tucson in Arizona is a busy university town.
It's home, among the cacti, to the scientists who ran NASA's Phoenix Lander on Mars, to astronomers who use telescopes like those on Kitt Peak and to the Arizona Wildcats.
You'd expect any American university worth its salt to have a pretty impressive football stadium, but this one's special.
Beneath me is the world's most advanced telescope mirror laboratory.
The heart of any telescope is its mirror, and as far as mirrors go, size definitely matters.
The more light they collect, the better the image is.
But size comes at a cost.
Big mirrors are heavy, requiring lots of support as they're swung around the sky.
Here at the Steward Mirror Lab, they have a novel way to make big mirrors that are a fraction of the weight.
Dr Peter Wehinger told me how.
What's behind us is a casting for what is the world's largest piece of glass that will go into a telescope called the Large Synoptic Survey Telescope, LSST.
What stage is this mirror at and what's happened to it already? We start out with a set of hexagonal columns.
I can see those still in They're roughly a metre in height and there are some 1,700 of these columns, they're alumina-silica, and they simply serve as a mould to create a honeycomb structure and we install something in the vicinity of 23 metric tonnes of glass on top of the hexagonal columns, and it takes about a million watts of power to heat the glass 24-7 and at the end of a week the glass is liquid and it seeps between the hexagonal columns and produces a honeycomb structure with a layer of glass on the bottom and another layer on the top and vertical columns in between.
What's this structure on top of the mirror? The circular discs and the steelwork above it are basically all part of a distributed lifting device that will enable us to lift the glass right from the front surface.
So we have something called RTV silicone rubber Bathroom sealant, right? Yes, and it works very well.
And then the steelwork above it is simply a means of distributing the weight over the whole 23 tonnes.
LSST is due to look at the sky for the first time in 2014? 2014-15, something in that And yet it's only 2008.
Does it really take that long to make a mirror? Typically, it takes about three and a half to four years to produce a single mirror.
We typically, in the mirror lab, have several mirrors in various stages of casting, grinding, polishing and so forth.
Earlier this year, The Sky At Night filmed up the road at the Large Binocular Telescope, or LBT.
Its two mirrors were both made in the Steward Mirror Lab.
The LBT is itself the prototype for a truly enormous beast It will have not 2, but 7 mirrors and is due for completion in 2017.
It may seem a long way away now, but here in Tucson one of the mirrors destined for that telescope is already nearly complete.
The team here are using the latest technology to produce their mirrors.
It's incredibly high-tech.
The motivation is the same as it's always been.
astronomers want bigger and better telescopes to look further into the universe.
Roger Angel is the mastermind behind the design of these mirrors, drawing inspiration from the long line of scientific mirror makers stretching back through the ages.
This is a mixture of very old technology that would be very familiar to Newton and Galileo and very new technology that allows us to go so big, and so on.
The part that would be instantly recognised by those guys is the fact that when we polish the glass, the actual what contacts the glass is pitch and that's exactly what Galileo and Newton used.
So after 400 years, we're still using the same material that actually rubs the glass that they used so long ago.
If you put a plate with pitch on the bottom of the glass and wait for a bit, after a few days it will fit exactly the glass.
Now if you rub that plate around the glass, if it's got bumps in it then as you move the pitch around all the high bumps on the pitch and the glass will get worn away by the polishing compound.
The motion keeps finding the high spots.
Galileo was able to make a lens whose surface was accurate to a millionth of an inch.
Now people have gone back, looked at Galileo's lenses.
They're fabulously accurate.
Here's a time where there were no machines tools, nothing of any accuracy, and yet this process, because the pitch smoothes out and flows out and you move it over the glass, makes this hugely accurate surface.
You can build mirrors up to 8.
4 metres in diameter.
Is that a maximum size? Well, when we wrote the first paper suggesting these mirrors about 30 years ago, we set 8 metres as the size of the freeway, because we can make a mirror perhaps bigger than this, but if you need to get it to the highest mountain top and it's got to go on a boat, and particularly on the freeway, so when these mirrors leave, we block one direction of the freeway.
All the traffic is held up until the truck gets off the road.
This is about the limit of transportation.
It's awe-inspiring to watch these giant mirrors rolling off the production line and it makes my mouth water to imagine what they'll see as they light the way forward for astronomy.
We use telescopes to look at the sky, but what about the sun? Can we use telescopes there? The answer is yes.
Galileo did and did it sensibly.
But you've got to be careful.
The sun is dangerous.
So here's Pete Lawrence to explain how to observe the sun, safely.
When you think of a telescope, you probably think of one used for night-time observing, looking at the stars.
But of course, telescopes can also be used during the day.
The sun presents a fantastic opportunity to see a star in close-up.
So, how do you look at the sun with a telescope? There are various ways of doing it safely.
Because the sun gives out a lot of light, heat and energy, if you don't do it correctly, you may damage your equipment, or worse, your eyesight.
So, let's look at a few ways of looking at the sun.
One of these is to use projection.
To do this, you point the telescope at the sun, let the sunlight come through the telescope and onto white paper or card.
When that happens, you have an image of the sun appearing on the card.
That's an extremely safe way to look at our nearest star.
But there is a danger and you must be aware that if you have a finder on your telescope, this too acts like a little projection telescope, so the best thing to do is to remove the finder completely.
Then there's no danger of heat build-up at the back of the finder.
Not all telescopes are suitable for looking at the sun like that.
Reflecting telescopes or Schmidt-Cassegrain telescopes aren't, because there's a heat build-up close to the secondary mirror and if the secondary mirror gets hot, it can shatter and break and then fall down onto the primary.
So the best type of telescope is, undoubtedly, a refracting telescope, a lens-based telescope, to project the sun.
Another way to look at the sun safely and this way encompasses other types of telescope, reflectors, Schmidt-Cassegrains and refractors, is to use special Astro Solar film.
It's a piece of aluminized Mylar that fits over the front of the telescope.
You buy it in sheets, A4 size, which are about £15 a go, make your own filter and then make sure you can attach it securely to the front of the telescope.
If the wind blows the filter off, then you could be in real trouble, so it has to be firmly fixed.
It's a good idea to check the filter before you put it on, by holding it up to the sun to make sure there are no holes in it, letting light through.
When you look at the sun using a filter, you're looking at it in what's called white light.
If you want to see the sun in a different, more exotic light, we have to use a speciality filter.
I have a hydrogen alpha telescope here.
It's a relatively small, inexpensive one - about £500 or so.
This will filter the sun so we block out most of the light, but we're just looking at it in the light of hydrogen alpha.
This lets us see burning, glowing hydrogen on and around the sun.
Using a filter like this, we can see prominences leaping off the side of the sun and dark, snaking filaments, edging their way across the sun.
If you have a normal telescope, like this, and you wanted to convert it to be a hydrogen alpha telescope, you can do that as well.
You have to buy a speciality filter, such as this, which fits on the front of the telescope and that converts the telescope into a hydrogen alpha telescope.
You can look through it using a special blocking filter, which goes in at this end and together, they allow you to view through the telescope, directly at the sun and see all these wonderful, exotic hydrogen alpha features.
So, whatever method you use to look at the sun, do it safely and enjoy the wonderful views afforded by our nearest star.
These are ground-based telescopes, but now let's turn to space.
And that means the Hubble Space Telescope, launched in 1990.
A little while ago, I talked to two people deeply concerned, Professor Martin Barstow and astronaut Professor Jeff Hoffman, who's been to the telescope.
Three, two, one and lift-off for the space shuttle Discovery with the Hubble Space Telescope, our window on the universe.
At one day, 43 minutes, mission elapsed time, this is Hubble Telescope Control.
Otherwise everything going very smoothly here at the Space Telescope control centre.
Congratulations on a super mission and the world is looking forward to reaping the benefits of your good work over the next 15 years.
The Hubble Space Telescope, still going strong.
Jeff, may I come to you first? You've been to Hubble.
Must've been a great experience.
It's 15 years since our initial rescue repair mission to Hubble.
Hubble has been such an incredible success over all that time that I think many people forget what a disaster it was, right after launch, when we discovered the optical problem.
The despair, the outrage that the astronomical community, the public at large, Congress and the United States felt.
NASA was really in a crisis, and I was fortunate enough to have been on the mission that saved Hubble.
Do you know exactly what the trouble was? It turns out it was a spherical aberration of the main mirror, which is a very, very common error in amateur telescope making.
By a tiny amount? The amount of extra glass they removed from the outside of the mirror was about one micron.
That's about one-50th the diameter of an average human hair.
Very tiny, but it shows the precision with which Hubble operates, that just that tiny amount made it impossible to get good focus out of the Hubble optics.
When you got to Hubble, what was your actual role? Our actual mission followed several years of painstaking analysis by astronomers and optical engineers where they figured out what the problem was and then developed very clever ways of installing corrective optics.
Our job was to install those corrective optics, as well as correct several other problems, because several things had failed on Hubble.
We had to replace some of the gyroscopes, we had to replace some of the fuses and electronic boxes.
But the most important thing was to get the optics fixed.
That meant space walking, of course.
One of the remarkable things about Hubble was that it was designed from the beginning to be serviceable by space-walking astronauts.
That meant you can operate Hubble much in the same way as ground-based telescopes, where you build a telescope, they have a mirror, the mirror is then fixed, but as years go by and detector technology improves, you continually upgrade the detectors you put at the focal point.
This had never been possible with telescopes in space before, and Hubble was unique because of that ability.
We used that capability to remove and install instruments with high precision to actually be able to install the corrective optics.
You're essentially an X-ray astronomer, aren't you? That's what I started out as in my early career, but once I went to NASA, I realised I wasn't there to do research and I have to say that to have been able to fix Hubble and make it available once again for the astronomical community, I probably made more of a contribution to astronomy than I would've had I continued to do research.
Jeff, it must be a magnificent experience to go to Hubble.
I was very lucky.
As an astronomer and an astronaut, to put my hands on Hubble, in its working environment - which is in space - was the thrill of a lifetime.
It doesn't get any better.
All right, let's just look at the seal.
My side looks good.
Mine's beautiful.
OK.
Martin, the next repair mission is now being actively planned.
What's it going to do, actually? There are several really important things we have to do on the next mission.
The gyros have to be replaced again.
We're always replacing gyros, because they fail fairly frequently.
They're relatively fragile things.
I now know more about gyros than I ever wanted to know! But for me, more excitingly, is the installation of two new instruments - the Cosmic Origins Spectrograph, which is an ultraviolet spectrograph and the third Wide Field Camera, Wide Field Camera 3, which will replace the Wide Field Planetary Camera 2 that Jeff installed all those years ago.
I'll be looking forward to seeing that when they bring it back on the ground, get my hands back on it! I think the other important elements are not new instruments but repairs to old ones.
Both the Space Telescope Imaging Spectrograph and the Advanced Camera for Surveys suffered failures.
They're very important instruments still.
There are plans to repair both of those, which we hope will be successful.
They will be among the most challenging parts of the mission.
And last but not least is the repair to the Command and Data Handling System which failed just before the planned launch for the servicing mission last October.
Without that, nothing else will work effectively, because we don't have any redundancy at the moment in this particular system.
and that must be replaced to make sure we have the planned lifetime.
This will probably be the most challenging servicing mission yet.
The number of things they have to do and the limited number of spacewalks they have to fit in is going to make it difficult.
There isn't room for any problems.
We have come to expect 100% success for this mission, but that doesn't mean it comes easy.
You can't relax when planning for these missions.
As Martin said, some of the things they'll try on this mission have never been attempted before.
They're going to take apart an electronic box, and make a repair on the board level, pull out an electronics board and put a new one in.
This was never imagined when Hubble was designed.
It's extraordinary.
There was a nice analogy about the ACS repair - the Advanced Camera for Surveys - it's like a heart bypass.
We're taking up a new piece of electronics to strap across the old one, to try and bypass the failed area.
How much lifetime do you think you've got? We would hope and expect that it'll go on till at least 2015.
A big aim at the moment is to plan for an overlap with the James Webb space telescope so that we have what is billed as Hubble's successor, although those of us in UV and optical astronomy don't agree so much, we'll have those in space at the same time working together, which would be immensely powerful.
Hubble went up in 1990.
It's still there.
It's pioneered space telescopes, been an outstanding success.
Absolutely.
I agree wholeheartedly.
We were thinking earlier on about all the amazing things it's done - the monitoring of the explosion on V838 Monocerotis and the fantastic images of the light echo as that shockwave has spread out and the light reflecting back from the surrounding gas has successively come back from the different parts of the material that's been thrown off.
One of my other highlights was the spectroscopy of an extra solar planet, which was a remarkable piece of science that you'd never have anticipated Hubble would have been able to do when it was launched.
Jeff, what's your favourite Hubble picture? I would have to say that the ability to pick out the supernova far away in the universe that's led us to appreciate the fact that the expansion of the universe is actually accelerating.
It was completely unexpected and has changed our view of cosmology completely.
Hubble has done so many things, but if I had to pick just one, that's what it would be.
Well, certainly, Hubble is still in a class of its own.
It's been a magnificent success.
Thank you both for joining us.
Thank you.
Always a pleasure.
It's always a pleasure, Patrick.
You know, Hubble's taken marvellous pictures.
Everyone's got their own particular favourites.
Mine happen to be of Mars, but others may have different ideas.
We've been asking our contributors to select their favourite pictures.
And here are the results.
My favourite Hubble image is of Abell 2218.
Abell is a cluster catalogue - clusters are large groups of galaxies in the universe.
And this, for me, was the most spectacular demonstration of gravitational lensing.
So, you have this big galaxy in the middle and around it, you have little, tiny arcs.
Each one of those arcs is a distant galaxy that has been perturbed as the light comes from behind the cluster.
For me, you needed the resolution of a space telescope to see these fine details.
You see behind me my favourite Hubble image.
It's the Hubble Ultra Deep Field.
It's the deepest picture ever taken of the universe.
What happened was, the Hubble Space Telescope opened its shutter and took a three-month long exposure of a dark patch of sky that had essentially nothing in it.
And instead of seeing nothing, the Hubble Space Telescope saw 10,000 galaxies.
My favourite Hubble image is the one that shows Saturn - not only the rings of Saturn, but the aurora, both at the north and south pole.
I have a rather soft spot for Saturn, because I have an instrument on the Cassini Spacecraft, but the reason I like the auroral image is you can see it standing up off the North Pole.
It shows you red and white, so you can see helium and hydrogen in the atmosphere, so I think it's spectacular.
I actually worked on one of the instruments, for Hubble, and that was the faint object camera.
The image that I remember was the image of Pluto, and for the first time, showed it as more than just a mere dot.
And it became, at least to me, it seemed like a real object, with character.
I think the most amazing results from Hubble have come when it's given us glimpses of solar systems forming around other stars.
Look deep into the heart of the Orion Nebula with the Hubble Space Telescope and you see not only stars but these strange objects.
These are proplyds, dusty disks silhouetted against the bright background gas.
From these disks, planets will form.
Or look at this disk around the bright star Fomalhaut.
Look into the disk, and you see a planet, formed and moving around its parent star.
Our first glimpse of another world.
My favourite Hubble image is the wide-field view of the Whirlpool Galaxy M51.
What I find amazing is that even though this galaxy is 37 million light years away, Hubble reveals all those wonderful pink starburst regions along the spiral arms, and you can actually see the way the smaller galaxy is distorting the structure of the spiral arms of the larger neighbour.
That's why I think it is an amazing image.
It would have to be the Pillars of Creation.
That, to me, symbolised the first of the Hubble images that started to come through that gave this completely new vision of the cosmos.
It was fascinating to think that in these three sticks of candyfloss, this is where stars are forming.
This was what you could do with Hubble.
Well, now let's come back to Earth.
What will telescopes of the future look like? Well, here's the Hobby-Eberly Telescope in Texas.
Chris went there.
I set off this morning from El Paso, in the far southwest of Texas, driving alongside the Mexican border.
The road is on a gentle incline, because my final destination is the Davis mountain range, which, at 10,000 feet, offers some of the darkest skies anywhere in the continental United States.
The McDonald Observatory has been perched on top of Mount Locke and Mount Fowlkes for the past 76 years and is now run by the University of Texas.
The two oldest telescopes here are the Otto Struve, built in 1933, and the Harlan J Smith Telescope, which dates from 1966.
Their newest companion, which I've travelled to see, is the Hobby-Eberly Telescope.
Astronomers are greedy.
We always want bigger telescopes to give us more light so we can see fainter objects.
The silver dome behind me contains a telescope that's not only large, but also rather special.
The design of the Hobby-Eberly Telescope, which was completed in 1997, is revolutionary.
It's still the third largest astronomical mirror in the world, but was built at a fraction of the cost of a normal telescope of this size.
The reason is its mount.
On the next mountain over, director David Lambert is operating one of the older telescopes.
Its heavy mirror needs a strong mount so it can be supported properly when it's pointed at the sky.
The larger the mirror, the more difficult and costly this becomes.
Solving these problems is not only difficult, it's expensive.
But here at the Hobby-Eberly telescope, they've come up with a radical, cheaper solution.
The giant mirror stays fixed, and the sky turns above it.
This is made up of 91 identical segments about one metre across.
The goal is to make a very large mirror, in this case 11 metres across.
Can you imagine making an 11-metre piece of glass? It's heavy, and it's very difficult to transport and manoeuvre.
When this was finished in '97, it was the third largest in the world.
How do you keep the segments in position? At the beginning of the night, we point the telescope to a tall tower outside, and there's a laser up in the tall tower which fires down at the 91 mirrors.
And then there's a computer program, and adjustments behind each mirror that allow us to align the 91 images on top of each other.
Up above the giant mirror, a secondary moves to follow objects in the sky for a short while.
It works well, but compromise comes at a price.
Not all of the sky is visible to the telescope.
The telescope was designed from the very beginning to have a structure containing the optics that is fixed at an angle, in this case, of 35°.
So this mirror always stays at this angle? It always stays at this angle.
That was a cost saving.
We saved probably 80% of the cost of making the same size telescope fully steerable.
You don't need this huge mount that can swing around? We don't need the mount, the motors, the engineering.
The cost, of course, is that we can only observe objects that are in a ring 35 degrees off the vertical.
That ring, because of the motion of the tracker, has a width of about plus or minus 8 degrees.
So over the course of a year, 70% of the sky passes through the ring.
How long can you observe a single object for? That depends on where the telescope is pointing.
Looking due south, it's about 45 minutes.
If we're looking due north, it approaches two to three hours.
The other beautiful tweak to the telescope design is in the way it rotates.
The telescope, during an observation, is resting on four of these feet, which are resting on this concrete pillar.
After an observation, we want to point to a different point, north, south, east and west, so the telescope 100-tonne structure is, as you can see, getting an inch off this concrete.
Supported just by? It's supported by 8 of these airbags, 20lbs per square inch.
Wow! Like a little hovercraft.
Put your hand here, you can feel the air coming out.
You really can! So the telescope, during the night, is operated by the telescope operator from the control room.
It moves round this concrete pillar, the computer tells the telescope structure when it's at the right compass point and then the air is cut off and the telescope comes back down.
This foot comes back down.
How quickly can you move from one object to another? That's always crucial.
Well, the design was just a few minutes, so we don't lose very much time.
The telescope specialises not in taking images, but in using an instrument called a spectrograph.
This splits the light from objects into their constituent colours, telling us what stars and other objects are made of.
David took me to the Observatory's new visitor centre, which uses light from the sun to explain what the spectrograph does.
We're producing an image of the sun and the image is projected from a telescope on the roof of a building.
From the image of the sun, a little slot of light is fed back to a diffraction grating - think of it as a prism - it spreads the light out into a spectrum, a rainbow of colours, and that's what you see projected.
As well as the rainbow from violet through to red, I can see dark lines in the spectrum.
They're important.
We call these Fraunhofer or absorption lines and they are produced by atoms of different chemical elements in the atmosphere of the sun absorbing some of the light.
So, from those lines, we can trace out which elements are present, which are not and determine also the amount of those elements, things like the temperature and pressure and the velocity flows in the atmosphere of the sun.
With the power of the Hobby-Eberly's giant mirror behind them, astronomers have used a spectrograph to study stars sprinkled throughout the galaxy.
So what can the Hobby-Eberly Telescope tell us about stars in our galaxy? Because of the large aperture, the telescope can look at quite faint stars, and we have the high-resolution spectrograph in the basement, so one can determine whether there's a correlation between the metal content, as we say in astronomy, and the motions of the stars, an ultimate lead to clues as to how the galaxy was assembled.
In a star like the Sun, the metals make up less than 2% of the mass of the star.
And they come from previous generations? They come from previous generations of stars by nuclear reactions inside the hot interiors of stars.
There are then processes, usually explosions, that get those elements out into the interstellar medium and new stars form containing these metals, or contaminants.
I know you've looked for some of the metal-poor stars, those which are relatively pristine.
Why are they special? Because they were formed early on.
The search right now is to find the most metal-poor stars.
There have been recent discoveries where the metal content is one part in 10 to the 5th.
That's one part in 100,000? Correct.
And those stars, possibly, formed from gas that was contaminated only by the very first generation of stars to form from the Big Bang, and they were very special stars because they only contained hydrogen and helium.
I've been to many observatories around the world, but I've never seen anything quite like the Hobby-Eberly Telescope.
It may only be able to see a fraction of the sky, but the ingenuity of its design is hard to beat.
Every telescope, every observatory has its own story, from the new technology of the Hobby-Eberly behind me to the amazing legacy of Kitt Peak, with a new generation of giant telescopes already under construction, I'm sure the most amazing stories are still to be written.
And that takes us on to the future.
Where do you think the future lies? Well, the future does lie with segmented mirror telescopes.
Three groups are planning larger telescopes than the Hobby-Eberly and the Keck Telescopes and all of them involve segmented mirrors.
So, starting with the Thirty Metre Telescope - this is a collaboration between Caltech, the University of California, Canada and Japan and the segments themselves - there will be 490 of them.
So a telescope of that aperture is really very, very powerful.
One of the driving forces is to study galaxies at the very edge of the universe, perhaps the first generation of galaxies to switch on, when the universe is only 3-4% of its present age.
What about the atmosphere? We have to get rid of the atmosphere, because it blurs the signal.
Fortunately, adaptive optics has made tremendous progress over the last 10 years.
It's quite challenging to correct for the blurring over the big aperture like a 30-metre diameter.
How exactly do you do it? The way it works is, you shine a sodium laser beam into the sky along the direction of the object you're interested in observing, and this reflects off sodium atoms high in the atmosphere.
Which are there already? Which are there already, and they create a spot of light which is effectively an artificial star.
We monitor the signal from that artificial star and correct for the blurring using a deformable mirror, a small mirror made of many components, each of which can be moved independently.
How many corrections per second? It's several corrections per second, and these deformable mirrors have several hundred individual components.
So the technology is demanding, but the progress has been so great that we're now optimistic it can be applied to these larger telescopes.
So the other telescopes are the European Extremely Large Telescope - this is a 42-metre telescope.
That is really a balance between the amount of money that ESO thinks it can raise for a telescope of this aperture and the desire to have even better performance than the Thirty Metre Telescope.
The final project, which is quite exciting, is the Giant Magellan Telescope.
So it's an exciting time, driven by fundamental scientific questions, such as imaging extrasolar planets, looking at the earliest objects in the universe and, of course, studying cosmology and dark matter and the fundamental questions of the origin of life and the nature of the universe that we live in.
Well, Richard, why the quest for even bigger telescopes? It never ends, Patrick.
George Ellery Hale once said, "Light is falling on the Earth from all over the sky "and all we can do is collect the bit that lands on 100 inches across.
" He was driven to build bigger and bigger telescopes to learn more about the universe - the quest never ends.
The technology enables us to do it.
It's a very exciting future.
Richard, thank you very much.
Thank you.
We began the series way back in April 1957 and look how much has happened since then.
Despite all the electronics, visual photography is still used for some branches of research.
David Malin, who came to Siding Spring as a photographer, spends his observing time in a cage at the fine focus.
The official name of the observatory is El Observatorio del Roque de los Muchachos.
I'm afraid my Spanish accent isn't very good, but here are Los Muchachos, the two boys.
I'm sure there is a local legend about them, but no-one seems to know it! There is the moon.
I can see it for the moment.
No, it's gone again.
It's gone.
Infuriating.
There's nothing one can do.
The heart of any telescope is its mirror, and here we have the 4-metre or 158-inch mirror of the main telescope on Cerro Tololo.
It really is enormous.
It's two foot thick, and it weighs 15 tonnes.
We're clouded out here.
There is sometimes wait a moment There's a break over there - can you see? I can't see anything in it, though.
No.
This neat and efficient-looking dome contains a 10" reflecting telescope.
Just to make sure we know where we are, the latitude and longitude's on the door.
The Royal Greenwich Observatory gave it to me to pinpoint my position if I sent in any observations.
Do you find that the dome's easy to turn? Once you get it going, Patrick, it's quite easy.
See? Just you have a try.
Yes Oh, that's pretty easy.
There's no difficulty there.
There's still a lot of drifting cloud up there and we can't tell if it'll be obscured at the critical moment.
You won't see Vega looking large, because no telescope will show It's gone, Patrick.
Has it gone? Oh, no! Just as I got it on the cross wires, it blacked right out.
How typical! Nothing we can do.
The next morning, there was a 70mph gale, and when I arrived the wind was really tremendous.
It was just as much as I could do to open the door to get inside the Great Dome.
Astronomy is unlike anything else, and one can give as much time to it as one wants.
You can get a tremendous amount of enjoyment and if you do useful work too, so much the better.
Good night.
Good night.
And so, from Brighton, where the sky is now completely overcast, good night.
Good night.
Well, I think you'll agree, it's a wonderful story.
We've come so far in the last 400 years, from the tiny telescopes of Galileo's time through to the huge telescopes now.
We can look back into the depths of the universe.
It's a story well worth telling.
I hope you've enjoyed our look back at the history of the telescope.
This is where I have my home and my telescopes, including my beloved 12.
5 inch reflector.
In this special programme, we're going to look at 400 years of the telescope in astronomy.
It's a marvellous story and over the years, we've been to some of the world's great observatories.
100 years ago, the world's largest telescope was the great reflector set up by the Third Earl of Rosse at Birr Castle in Ireland.
The telescope was completed in 1845.
We're going to talk about it in this evening's Sky At Night.
I am standing on top of one of the most remarkable telescopes in the world.
We're at Kitt Peak in Arizona.
Mount Wilson is one of the peaks overlooking Los Angeles.
It's 5,700 feet high.
Nothing special.
And outwardly there's nothing to mark it out.
La Palma is now becoming famous in another direction.
It's here that one of the world's great observatories is being set up.
The great 28-inch telescope is coming home where it belongs at the Old Royal Observatory in Greenwich Park.
Sun-soaked palms and temperatures in the mid-80s, but there's another angle to Hawaii too.
A region of thin air, icy cold and winds up to 150 mph.
And that's where I am now.
On the top of Mauna Kea, nearly 1,400 feet above sea level.
Its great strength lay in its light-gathering power which was greater than any other telescope until that time.
In astronomy you want to see very faint things.
To see faint things you need as much light as you can get.
The bigger the mirror, the more light you can collect.
This is where the big Rosse mirror came in.
Even with the naked eye, you can carry out a great deal of work in astronomy.
But of course, the telescope makes all the difference.
So who made the first telescopes and who first turned them skyward? Most people say Galileo.
Well, I talked to one of our regular guests, Dr Allan Chapman, who has other ideas.
All that we can say is on the 2nd October, 1608 a German living in Holland, in Middelburg called Hans Lipperhey presented a petition to the state's general, the Dutch government, for a device that made distant objects appear close using a pair of lenses.
The thing is he didn't get his petition or his claim, because two other Dutchmen immediately leapt in and said, "We've got the device too", so actually we don't know.
The key thing is though, what happens is this is the first use of the telescope in the world.
Now because he didn't get a patent claim, very quickly these devices went on sale across Europe.
They were on sale in Frankfurt, Paris and various other places by the end of 1608.
Now an Englishman called Thomas Harriot acquired one from somewhere.
He called it his "Dutch trunk" and what the original device was was a pair of lenses in a tube.
An object glass and an eyepiece.
The object glass has to be thicker on both sides.
It has to be convex.
They eye piece has to be narrower in the middle - a concave.
Put them both in the right positions and "boom!" - suddenly distant objects are very close.
Now what the Dutch were using it for was to look at ships or distant buildings.
The Dutch of course at that time were in a war of liberation against Spain.
Useful strategic device.
But Harriot uses them scientifically.
On the 26th July, 1609, he looked at the five-day moon.
So Harriot was the first telescopic astronomer.
Without any doubt.
Or the first one on written record.
What his telescope looked like was something like this.
I made this replica which is the same as the two lenses object glass at this end, eyepiece there.
And this magnifies about 20 times.
When I look at the moon with this, I can see the main craters.
One or two known points but certainly the Mare Nectaris the Mare Tranquillitatis on one or two features.
And then all of a sudden the realisation is the telescope shows you things you can't see without it.
And over the course of about a year and half, Harriot makes a series of maps.
Now it's true by the summer of 1610, he would have had Galileo's observations, which had been published in Venice in March 1610 and on sale in England in June of that year, but also too, Harriot is making better drawings of the moon than anything in Galileo, and then he makes an undated map, but certainly around 1610-11, of the whole moon.
And that is a stunningly beautiful map.
It is.
It has the seas, it has lots of prominent craters.
He had no idea what he was looking at.
He didn't quite know what the whole moon was made of, but as a piece of cartography, it was superb.
These early telescopes were refractors then we come to reflectors.
And this little telescope, this brass instrument on loan from the Science Museum is of the Gregorian pattern.
This is how a Gregorian worked.
Very kindly, the Science Museum has provided us with a cutaway instrument.
As these are nearly 200 years old, we handle them with white gloves so acids from our fingers won't affect the metal.
You have a parabolic mirror down here.
The light comes in, hits that mirror is reflected back up to a second mirror it's then reflected back down through a hole in the main mirror and to an eyepiece.
Once you've got the reflecting system you are able to see bigger, brighter images.
because it was easier to make big mirrors than big lenses.
What William Herschel called space penetrating power.
They realised very early on when you make a more powerful telescope, you see more stars, more stars, more stars.
Is the universe infinite? Does it go on forever? The telescope is the first instrument that shows us we can see things beyond our five senses.
And we think the telescope, the microscope, the barometer In more recent times, photography, digital imagery, TV.
I suggest the telescope is the first that shows us we can go beyond normal vision.
In that respect, it's transformative in so many ways.
This is my main telescope, my 15-inch reflector.
Well, here at Selsey, conditions are as good as they are anywhere in England, but of course, they're not perfect and the world's big observatories have to be very carefully sited.
One of these is Kitt Peak in Arizona, and Chris went there.
Deep in the Arizona desert, 40 miles away from the bright lights of Tucson, is a world-famous collection of telescopes.
Astronomers first came here more than 50 years ago for the clear skies and the dry air.
From a distance, you can still see the sparkle of the silver and white domes, gleaming in the relentless sunshine.
Welcome to Kitt Peak, America's national observatory.
With 25 or so domes scattered across the mountain top, this is the largest collection of professional telescopes anywhere on the planet.
The largest of the more than 25 telescopes here can be used by astronomers from any university or any country.
This is the home of Astronomy for All.
Down in Tucson is the National Optical Astronomical Observatory, which is in charge of Kitt Peak.
It shares a campus with the University of Arizona, and as students walk to class, I talk to Doug Isbell about the early days on Kitt Peak.
So how long have there been telescopes on Kitt Peak? Well, it was 50 years ago that Kitt Peak was elected as the site of the US National Observatory after a search across the continent.
About 150 sites were looked at, and Kitt Peak was selected due to its very clear, dry weather, its overall good climate, its dark skies and also it was close to practical things like a university, and an airport where the scientists could fly in from their universities, which were largely in the East.
It was founded to give Eastern and mid-Western scientists a place to do astronomy with dark skies.
So what was on the mountain before the astronomers arrived? We're on the land of the Native American Tohono O'odham Nation, separate from the United States in many respects, and we're a tenant there.
We're honoured to be on their land.
We have a long-term lease through the National Science Foundation with the Tohono O'odham Nation.
On the mountain, the telescopes are being prepared for the night.
In charge of the oldest large telescope on the mountain, the 2.
1 metre, is Dr Howard Bond.
When the telescope was new, he would've been assisted by an operator, but now he has to do everything himself.
Times have changed! It was with this telescope that astronomers were first able to probe the fingerprints of hydrogen in distant galaxies, helping them piece together the history of the universe.
Today, Howard is using the telescope to follow up on observations made using the Hubble Space Telescope.
Tonight, we're working on a programme that's related to the Hubble Space Telescope.
So with Hubble, we're measuring the distances to stars using the parallax effect.
Those measurements are relative to surrounding background stars, and to get an absolute true distance, we need to make an estimate of how far away those background stars are.
To do that we measure their brightnesses and colours, which is a perfect thing for a ground-based telescope, like the 2.
1-metre telescope that you see behind you.
These are relatively local, it's surprising we don't know the distance well already.
Why do we need to know so accurately how far away these stars are? The problem is we use these Cepheid variable stars, very bright stars and we know the brightness depends on the period of variation.
The question is setting the zero point.
There aren't any Cepheids that are close enough to the earth to have their parallaxes measured accurately with ground-based telescopes.
The nearest Cepheid variable is the North Star, Polaris, which I'll be observing tonight if the weather stays clear.
Hasn't Polaris been behaving oddly recently? Yes, its range of brightness has been going down.
Some people predicted it would stop being a variable star.
It's bottomed out and it's still varying at a low level.
Is this your first night on the telescope? This is my third night - no, it's my fourth! I've already had three.
So you've been living nocturnally? Trying to, yes.
If the skies stay clear, Howard will look at about 24 stars tonight to measure their brightness.
But this isn't the only telescope which will be working tonight.
This is the Mayall telescope, when it was built, the second largest optical telescope anywhere in the world, and still the largest on Kitt Peak.
Its giant, 4-metre mirror is used for everything from looking at the edge of the solar system to studying distant galaxies.
The designers of the Mayall telescope in the 1960s gave it a radical look.
The dome sits 92 feet above the ground in an attempt to keep it clear of turbulent air.
As with all telescopes, it's kept up to date with new cameras and instruments, but the control room still has something of the feel of the inside of a battleship.
Tonight, Dr Kimberly Herrmann is preparing to take a close look at some nearby galaxies.
When we look at spiral galaxies, the rotation curves gives us the total mass of the spiral galaxy, but how much of that mass is in the bulge, is in the disk and is in the dark matter halo, that's what we want to know.
By studying planetary nebulae, we can look at the motions in and out of the plane of the galaxy to determine the disk mass in the galaxy.
Why are we interested in the outer regions? There are some very strange things going on in the outer regions.
There seems to be more mass out there than we would expect.
I'm trying to see how much light is out there.
If there's enough light out there to explain the mass I'm finding.
Kitt Peak was born from a noble vision - that good ideas win you time on telescopes.
It was and is astronomy for all.
These historical telescopes may not often grab the headlines today.
They serve as work horses rather than show ponies, but it's the meticulous work done here, night after night, decade after decade, that slowly reveals what our universe is like.
Kitt Peak remains in the forefront.
There are other great telescopes too, those in Hawaii or the Atacama desert.
All of these were built in the latter half of the 20th century.
It's an impressive instrument.
As with most large reflectors, the tube is a skeleton, and the mounting is a massive horse shoe.
The main mirror is 154 inches in diameter, or 3.
9 metres if you prefer metric, and that puts it in the world's top six.
When the question of an observatory on the top of Mauna Kea was first discussed, I'm sure there must have been plenty of raised eyebrows.
The difficulties were obvious - inaccessibility and above all, the effects of altitude on the observers, but the challenge was taken up and it's an unqualified success.
When you're building a big telescope, I suppose about 50% of the problems are engineering and the other 50% are optical.
Obviously, the main component optically is the big mirror of the telescope.
This rather strange-looking construction is the aluminizing chamber, inside which the mirror is kept until it's ready to be put into the telescope.
This has been brought out for us.
We're some of the first people to see it like this.
When I began the Sky At Night series in 1957, the biggest telescope in the world with the 200 inch at Mount Palomar in California.
But of course the early 20th century was the period of the first great reflectors and great observatories.
With me, Professor Richard Ellis of Oxford.
Welcome back to the programme.
Thank you.
A great period, wasn't it? A fantastic century of discovery in astronomy.
The large telescopes are, without question, contributed an enormous amount.
They've really shaped our view of the universe.
If one imagines the expansion of the universe discovered with the 100 inch Telescope and understanding Stellar Evolution with the 200 inch.
And now the Keck and European large telescopes pushing the frontiers to the most distant galaxies that we can see.
There are have been various telescopes that have marked new developments.
One of these was the 100 inch at Mount Wilson.
Tor a long time, the most powerful in the world and in a class of its own.
Yes, from the period in the early '20s until after the Second World War, the 100 inch was the largest telescope in the world.
Probably its biggest discovery was the expansion of the universe.
By Hubble, of course.
By Edwin Hubble himself.
There were early work that showed galaxies were moving away from us but Hubble showed the distance to a galaxy is correlated with the speed with which it's moving away from us.
He had to use the 100 inch for that, no other telescope could do it.
That' right.
This means the universe had a beginning.
That really is a profound discovery.
Perhaps the most significant discovery of the 20th century.
Hale masterminded the 100 inch.
He wasn't satisfied.
He was an amazing man.
He founded Cal Tech and the American Astronomical Society.
He was a relentless raiser of money for large telescopes.
There were many problems faced, both financial and technical.
The 200 inch was an amazing challenge.
Making the mirror was the biggest challenge of all.
There were several attempts to cast the mirror.
In the end, they were successful.
And that mirror is still in use celebrating 60th anniversary of world-beating science this year.
It is still in use doing frontier work.
It's a good example of how a telescope is a lasting achievement.
Telescopes are not stagnant things.
They can be updated with new instruments, and the 200 inch is testimony to that.
What do you think are the major advances by British technology? Firstly the Anglo-Australian telescope.
A fantastic project.
3.
9 metre telescope in Coonabarabran, Australia.
Its probably biggest achievement was the Galaxy Redshift Survey.
The so-called 2-degree field Redshift survey.
That was a huge step forward in our understanding of how much mass there is in the universe, the nature of dark matter, and the distribution of galaxies of various kinds, spirals, ellipticals on large scales.
The William Herschel telescope is on a better site.
It's a magnificent technical achievement.
It has fantastic instruments, including faint object spectrographs which were able to look at gravitationally lensed galaxies.
This was an era when Hubble was launched and so there was a good synergy between the Herschel telescope and the Hubble space telescope.
I'm a big fan of UKIRT, a very cost-effective telescope, very cheap, on the summit of Mauna Kea which is now doing a big infra-red sky search but it has achieved a lot in infra-red astronomy.
I would argue British astronomy and the infra-red was in the world lead for a long period when UKIRT was the largest infra-red telescope in the world.
Coming on to the VLT, how involved are we in that? Britain is a full member of the European southern observatory for many years now and most British astronomers are doing their cutting edge work on the ESO VLT.
This is 4 eight-metre telescopes, tremendous versatility, some of the best instruments in the world, particularly for spectroscopy and the infra-red and in the optical region.
What are the greatest achievements of the Keck, do you think? Firstly, the discovery of the most distant galaxies, up to Redshift 7 and beyond.
where we're looking back, 90-95% way back to the Big Bang.
That's really one area where I think Keck has been supremely successful simply because it's got fast spectrographs and 10-metre aperture.
Then I would select gamma ray bursts, energetic explosions We didn't know whether they were, oh heaven forbid, we didn't even know if they were in the solar system, milky way or distant universe.
They're not! They're a long way away.
And so these are tremendously energetic bursts of activity when two black holes or a black hole and a neutron star merge.
Finally the accelerating universe, the use of supernovae as standard candles to trace the history of the expansion.
Are you happy about that? I'm involved, Patrick so yes.
I'm very excited and it's a remarkable result.
It was found independently by two teams.
So the expansion is accelerating.
The expansion is accelerating.
Why? We don't know why.
We give a label of Dark Energy to it but who knows what that means? There's a lot of enthusiasm now in the astronomy community to get to the bottom of this.
There's a good achievement from the Keck telescope.
We said for a long time the Rosse telescope was superb, then the 100 inch, then the 200 inch.
Would you now say the Keck telescope is ahead of any other? It's hard to say.
The Subaru 8-metre telescope and the ESO VL in the Gemini observatories all of them are doing frontier work.
Keck has a wonderful advantage by being slightly larger.
10 metres over 8 metres does matter.
It does.
It's 10 squared over 8 squared.
Of course, Keck has a head start because it was on the scene earlier.
Much of the early work was creamed off by the Keck telescope.
That gave California astronomers an advantage.
The essential part of the reflector is this main mirror.
Everything depends upon how good the mirror is.
Chris has been over in Arizona seeing how 21st-century mirrors are made.
Tucson in Arizona is a busy university town.
It's home, among the cacti, to the scientists who ran NASA's Phoenix Lander on Mars, to astronomers who use telescopes like those on Kitt Peak and to the Arizona Wildcats.
You'd expect any American university worth its salt to have a pretty impressive football stadium, but this one's special.
Beneath me is the world's most advanced telescope mirror laboratory.
The heart of any telescope is its mirror, and as far as mirrors go, size definitely matters.
The more light they collect, the better the image is.
But size comes at a cost.
Big mirrors are heavy, requiring lots of support as they're swung around the sky.
Here at the Steward Mirror Lab, they have a novel way to make big mirrors that are a fraction of the weight.
Dr Peter Wehinger told me how.
What's behind us is a casting for what is the world's largest piece of glass that will go into a telescope called the Large Synoptic Survey Telescope, LSST.
What stage is this mirror at and what's happened to it already? We start out with a set of hexagonal columns.
I can see those still in They're roughly a metre in height and there are some 1,700 of these columns, they're alumina-silica, and they simply serve as a mould to create a honeycomb structure and we install something in the vicinity of 23 metric tonnes of glass on top of the hexagonal columns, and it takes about a million watts of power to heat the glass 24-7 and at the end of a week the glass is liquid and it seeps between the hexagonal columns and produces a honeycomb structure with a layer of glass on the bottom and another layer on the top and vertical columns in between.
What's this structure on top of the mirror? The circular discs and the steelwork above it are basically all part of a distributed lifting device that will enable us to lift the glass right from the front surface.
So we have something called RTV silicone rubber Bathroom sealant, right? Yes, and it works very well.
And then the steelwork above it is simply a means of distributing the weight over the whole 23 tonnes.
LSST is due to look at the sky for the first time in 2014? 2014-15, something in that And yet it's only 2008.
Does it really take that long to make a mirror? Typically, it takes about three and a half to four years to produce a single mirror.
We typically, in the mirror lab, have several mirrors in various stages of casting, grinding, polishing and so forth.
Earlier this year, The Sky At Night filmed up the road at the Large Binocular Telescope, or LBT.
Its two mirrors were both made in the Steward Mirror Lab.
The LBT is itself the prototype for a truly enormous beast It will have not 2, but 7 mirrors and is due for completion in 2017.
It may seem a long way away now, but here in Tucson one of the mirrors destined for that telescope is already nearly complete.
The team here are using the latest technology to produce their mirrors.
It's incredibly high-tech.
The motivation is the same as it's always been.
astronomers want bigger and better telescopes to look further into the universe.
Roger Angel is the mastermind behind the design of these mirrors, drawing inspiration from the long line of scientific mirror makers stretching back through the ages.
This is a mixture of very old technology that would be very familiar to Newton and Galileo and very new technology that allows us to go so big, and so on.
The part that would be instantly recognised by those guys is the fact that when we polish the glass, the actual what contacts the glass is pitch and that's exactly what Galileo and Newton used.
So after 400 years, we're still using the same material that actually rubs the glass that they used so long ago.
If you put a plate with pitch on the bottom of the glass and wait for a bit, after a few days it will fit exactly the glass.
Now if you rub that plate around the glass, if it's got bumps in it then as you move the pitch around all the high bumps on the pitch and the glass will get worn away by the polishing compound.
The motion keeps finding the high spots.
Galileo was able to make a lens whose surface was accurate to a millionth of an inch.
Now people have gone back, looked at Galileo's lenses.
They're fabulously accurate.
Here's a time where there were no machines tools, nothing of any accuracy, and yet this process, because the pitch smoothes out and flows out and you move it over the glass, makes this hugely accurate surface.
You can build mirrors up to 8.
4 metres in diameter.
Is that a maximum size? Well, when we wrote the first paper suggesting these mirrors about 30 years ago, we set 8 metres as the size of the freeway, because we can make a mirror perhaps bigger than this, but if you need to get it to the highest mountain top and it's got to go on a boat, and particularly on the freeway, so when these mirrors leave, we block one direction of the freeway.
All the traffic is held up until the truck gets off the road.
This is about the limit of transportation.
It's awe-inspiring to watch these giant mirrors rolling off the production line and it makes my mouth water to imagine what they'll see as they light the way forward for astronomy.
We use telescopes to look at the sky, but what about the sun? Can we use telescopes there? The answer is yes.
Galileo did and did it sensibly.
But you've got to be careful.
The sun is dangerous.
So here's Pete Lawrence to explain how to observe the sun, safely.
When you think of a telescope, you probably think of one used for night-time observing, looking at the stars.
But of course, telescopes can also be used during the day.
The sun presents a fantastic opportunity to see a star in close-up.
So, how do you look at the sun with a telescope? There are various ways of doing it safely.
Because the sun gives out a lot of light, heat and energy, if you don't do it correctly, you may damage your equipment, or worse, your eyesight.
So, let's look at a few ways of looking at the sun.
One of these is to use projection.
To do this, you point the telescope at the sun, let the sunlight come through the telescope and onto white paper or card.
When that happens, you have an image of the sun appearing on the card.
That's an extremely safe way to look at our nearest star.
But there is a danger and you must be aware that if you have a finder on your telescope, this too acts like a little projection telescope, so the best thing to do is to remove the finder completely.
Then there's no danger of heat build-up at the back of the finder.
Not all telescopes are suitable for looking at the sun like that.
Reflecting telescopes or Schmidt-Cassegrain telescopes aren't, because there's a heat build-up close to the secondary mirror and if the secondary mirror gets hot, it can shatter and break and then fall down onto the primary.
So the best type of telescope is, undoubtedly, a refracting telescope, a lens-based telescope, to project the sun.
Another way to look at the sun safely and this way encompasses other types of telescope, reflectors, Schmidt-Cassegrains and refractors, is to use special Astro Solar film.
It's a piece of aluminized Mylar that fits over the front of the telescope.
You buy it in sheets, A4 size, which are about £15 a go, make your own filter and then make sure you can attach it securely to the front of the telescope.
If the wind blows the filter off, then you could be in real trouble, so it has to be firmly fixed.
It's a good idea to check the filter before you put it on, by holding it up to the sun to make sure there are no holes in it, letting light through.
When you look at the sun using a filter, you're looking at it in what's called white light.
If you want to see the sun in a different, more exotic light, we have to use a speciality filter.
I have a hydrogen alpha telescope here.
It's a relatively small, inexpensive one - about £500 or so.
This will filter the sun so we block out most of the light, but we're just looking at it in the light of hydrogen alpha.
This lets us see burning, glowing hydrogen on and around the sun.
Using a filter like this, we can see prominences leaping off the side of the sun and dark, snaking filaments, edging their way across the sun.
If you have a normal telescope, like this, and you wanted to convert it to be a hydrogen alpha telescope, you can do that as well.
You have to buy a speciality filter, such as this, which fits on the front of the telescope and that converts the telescope into a hydrogen alpha telescope.
You can look through it using a special blocking filter, which goes in at this end and together, they allow you to view through the telescope, directly at the sun and see all these wonderful, exotic hydrogen alpha features.
So, whatever method you use to look at the sun, do it safely and enjoy the wonderful views afforded by our nearest star.
These are ground-based telescopes, but now let's turn to space.
And that means the Hubble Space Telescope, launched in 1990.
A little while ago, I talked to two people deeply concerned, Professor Martin Barstow and astronaut Professor Jeff Hoffman, who's been to the telescope.
Three, two, one and lift-off for the space shuttle Discovery with the Hubble Space Telescope, our window on the universe.
At one day, 43 minutes, mission elapsed time, this is Hubble Telescope Control.
Otherwise everything going very smoothly here at the Space Telescope control centre.
Congratulations on a super mission and the world is looking forward to reaping the benefits of your good work over the next 15 years.
The Hubble Space Telescope, still going strong.
Jeff, may I come to you first? You've been to Hubble.
Must've been a great experience.
It's 15 years since our initial rescue repair mission to Hubble.
Hubble has been such an incredible success over all that time that I think many people forget what a disaster it was, right after launch, when we discovered the optical problem.
The despair, the outrage that the astronomical community, the public at large, Congress and the United States felt.
NASA was really in a crisis, and I was fortunate enough to have been on the mission that saved Hubble.
Do you know exactly what the trouble was? It turns out it was a spherical aberration of the main mirror, which is a very, very common error in amateur telescope making.
By a tiny amount? The amount of extra glass they removed from the outside of the mirror was about one micron.
That's about one-50th the diameter of an average human hair.
Very tiny, but it shows the precision with which Hubble operates, that just that tiny amount made it impossible to get good focus out of the Hubble optics.
When you got to Hubble, what was your actual role? Our actual mission followed several years of painstaking analysis by astronomers and optical engineers where they figured out what the problem was and then developed very clever ways of installing corrective optics.
Our job was to install those corrective optics, as well as correct several other problems, because several things had failed on Hubble.
We had to replace some of the gyroscopes, we had to replace some of the fuses and electronic boxes.
But the most important thing was to get the optics fixed.
That meant space walking, of course.
One of the remarkable things about Hubble was that it was designed from the beginning to be serviceable by space-walking astronauts.
That meant you can operate Hubble much in the same way as ground-based telescopes, where you build a telescope, they have a mirror, the mirror is then fixed, but as years go by and detector technology improves, you continually upgrade the detectors you put at the focal point.
This had never been possible with telescopes in space before, and Hubble was unique because of that ability.
We used that capability to remove and install instruments with high precision to actually be able to install the corrective optics.
You're essentially an X-ray astronomer, aren't you? That's what I started out as in my early career, but once I went to NASA, I realised I wasn't there to do research and I have to say that to have been able to fix Hubble and make it available once again for the astronomical community, I probably made more of a contribution to astronomy than I would've had I continued to do research.
Jeff, it must be a magnificent experience to go to Hubble.
I was very lucky.
As an astronomer and an astronaut, to put my hands on Hubble, in its working environment - which is in space - was the thrill of a lifetime.
It doesn't get any better.
All right, let's just look at the seal.
My side looks good.
Mine's beautiful.
OK.
Martin, the next repair mission is now being actively planned.
What's it going to do, actually? There are several really important things we have to do on the next mission.
The gyros have to be replaced again.
We're always replacing gyros, because they fail fairly frequently.
They're relatively fragile things.
I now know more about gyros than I ever wanted to know! But for me, more excitingly, is the installation of two new instruments - the Cosmic Origins Spectrograph, which is an ultraviolet spectrograph and the third Wide Field Camera, Wide Field Camera 3, which will replace the Wide Field Planetary Camera 2 that Jeff installed all those years ago.
I'll be looking forward to seeing that when they bring it back on the ground, get my hands back on it! I think the other important elements are not new instruments but repairs to old ones.
Both the Space Telescope Imaging Spectrograph and the Advanced Camera for Surveys suffered failures.
They're very important instruments still.
There are plans to repair both of those, which we hope will be successful.
They will be among the most challenging parts of the mission.
And last but not least is the repair to the Command and Data Handling System which failed just before the planned launch for the servicing mission last October.
Without that, nothing else will work effectively, because we don't have any redundancy at the moment in this particular system.
and that must be replaced to make sure we have the planned lifetime.
This will probably be the most challenging servicing mission yet.
The number of things they have to do and the limited number of spacewalks they have to fit in is going to make it difficult.
There isn't room for any problems.
We have come to expect 100% success for this mission, but that doesn't mean it comes easy.
You can't relax when planning for these missions.
As Martin said, some of the things they'll try on this mission have never been attempted before.
They're going to take apart an electronic box, and make a repair on the board level, pull out an electronics board and put a new one in.
This was never imagined when Hubble was designed.
It's extraordinary.
There was a nice analogy about the ACS repair - the Advanced Camera for Surveys - it's like a heart bypass.
We're taking up a new piece of electronics to strap across the old one, to try and bypass the failed area.
How much lifetime do you think you've got? We would hope and expect that it'll go on till at least 2015.
A big aim at the moment is to plan for an overlap with the James Webb space telescope so that we have what is billed as Hubble's successor, although those of us in UV and optical astronomy don't agree so much, we'll have those in space at the same time working together, which would be immensely powerful.
Hubble went up in 1990.
It's still there.
It's pioneered space telescopes, been an outstanding success.
Absolutely.
I agree wholeheartedly.
We were thinking earlier on about all the amazing things it's done - the monitoring of the explosion on V838 Monocerotis and the fantastic images of the light echo as that shockwave has spread out and the light reflecting back from the surrounding gas has successively come back from the different parts of the material that's been thrown off.
One of my other highlights was the spectroscopy of an extra solar planet, which was a remarkable piece of science that you'd never have anticipated Hubble would have been able to do when it was launched.
Jeff, what's your favourite Hubble picture? I would have to say that the ability to pick out the supernova far away in the universe that's led us to appreciate the fact that the expansion of the universe is actually accelerating.
It was completely unexpected and has changed our view of cosmology completely.
Hubble has done so many things, but if I had to pick just one, that's what it would be.
Well, certainly, Hubble is still in a class of its own.
It's been a magnificent success.
Thank you both for joining us.
Thank you.
Always a pleasure.
It's always a pleasure, Patrick.
You know, Hubble's taken marvellous pictures.
Everyone's got their own particular favourites.
Mine happen to be of Mars, but others may have different ideas.
We've been asking our contributors to select their favourite pictures.
And here are the results.
My favourite Hubble image is of Abell 2218.
Abell is a cluster catalogue - clusters are large groups of galaxies in the universe.
And this, for me, was the most spectacular demonstration of gravitational lensing.
So, you have this big galaxy in the middle and around it, you have little, tiny arcs.
Each one of those arcs is a distant galaxy that has been perturbed as the light comes from behind the cluster.
For me, you needed the resolution of a space telescope to see these fine details.
You see behind me my favourite Hubble image.
It's the Hubble Ultra Deep Field.
It's the deepest picture ever taken of the universe.
What happened was, the Hubble Space Telescope opened its shutter and took a three-month long exposure of a dark patch of sky that had essentially nothing in it.
And instead of seeing nothing, the Hubble Space Telescope saw 10,000 galaxies.
My favourite Hubble image is the one that shows Saturn - not only the rings of Saturn, but the aurora, both at the north and south pole.
I have a rather soft spot for Saturn, because I have an instrument on the Cassini Spacecraft, but the reason I like the auroral image is you can see it standing up off the North Pole.
It shows you red and white, so you can see helium and hydrogen in the atmosphere, so I think it's spectacular.
I actually worked on one of the instruments, for Hubble, and that was the faint object camera.
The image that I remember was the image of Pluto, and for the first time, showed it as more than just a mere dot.
And it became, at least to me, it seemed like a real object, with character.
I think the most amazing results from Hubble have come when it's given us glimpses of solar systems forming around other stars.
Look deep into the heart of the Orion Nebula with the Hubble Space Telescope and you see not only stars but these strange objects.
These are proplyds, dusty disks silhouetted against the bright background gas.
From these disks, planets will form.
Or look at this disk around the bright star Fomalhaut.
Look into the disk, and you see a planet, formed and moving around its parent star.
Our first glimpse of another world.
My favourite Hubble image is the wide-field view of the Whirlpool Galaxy M51.
What I find amazing is that even though this galaxy is 37 million light years away, Hubble reveals all those wonderful pink starburst regions along the spiral arms, and you can actually see the way the smaller galaxy is distorting the structure of the spiral arms of the larger neighbour.
That's why I think it is an amazing image.
It would have to be the Pillars of Creation.
That, to me, symbolised the first of the Hubble images that started to come through that gave this completely new vision of the cosmos.
It was fascinating to think that in these three sticks of candyfloss, this is where stars are forming.
This was what you could do with Hubble.
Well, now let's come back to Earth.
What will telescopes of the future look like? Well, here's the Hobby-Eberly Telescope in Texas.
Chris went there.
I set off this morning from El Paso, in the far southwest of Texas, driving alongside the Mexican border.
The road is on a gentle incline, because my final destination is the Davis mountain range, which, at 10,000 feet, offers some of the darkest skies anywhere in the continental United States.
The McDonald Observatory has been perched on top of Mount Locke and Mount Fowlkes for the past 76 years and is now run by the University of Texas.
The two oldest telescopes here are the Otto Struve, built in 1933, and the Harlan J Smith Telescope, which dates from 1966.
Their newest companion, which I've travelled to see, is the Hobby-Eberly Telescope.
Astronomers are greedy.
We always want bigger telescopes to give us more light so we can see fainter objects.
The silver dome behind me contains a telescope that's not only large, but also rather special.
The design of the Hobby-Eberly Telescope, which was completed in 1997, is revolutionary.
It's still the third largest astronomical mirror in the world, but was built at a fraction of the cost of a normal telescope of this size.
The reason is its mount.
On the next mountain over, director David Lambert is operating one of the older telescopes.
Its heavy mirror needs a strong mount so it can be supported properly when it's pointed at the sky.
The larger the mirror, the more difficult and costly this becomes.
Solving these problems is not only difficult, it's expensive.
But here at the Hobby-Eberly telescope, they've come up with a radical, cheaper solution.
The giant mirror stays fixed, and the sky turns above it.
This is made up of 91 identical segments about one metre across.
The goal is to make a very large mirror, in this case 11 metres across.
Can you imagine making an 11-metre piece of glass? It's heavy, and it's very difficult to transport and manoeuvre.
When this was finished in '97, it was the third largest in the world.
How do you keep the segments in position? At the beginning of the night, we point the telescope to a tall tower outside, and there's a laser up in the tall tower which fires down at the 91 mirrors.
And then there's a computer program, and adjustments behind each mirror that allow us to align the 91 images on top of each other.
Up above the giant mirror, a secondary moves to follow objects in the sky for a short while.
It works well, but compromise comes at a price.
Not all of the sky is visible to the telescope.
The telescope was designed from the very beginning to have a structure containing the optics that is fixed at an angle, in this case, of 35°.
So this mirror always stays at this angle? It always stays at this angle.
That was a cost saving.
We saved probably 80% of the cost of making the same size telescope fully steerable.
You don't need this huge mount that can swing around? We don't need the mount, the motors, the engineering.
The cost, of course, is that we can only observe objects that are in a ring 35 degrees off the vertical.
That ring, because of the motion of the tracker, has a width of about plus or minus 8 degrees.
So over the course of a year, 70% of the sky passes through the ring.
How long can you observe a single object for? That depends on where the telescope is pointing.
Looking due south, it's about 45 minutes.
If we're looking due north, it approaches two to three hours.
The other beautiful tweak to the telescope design is in the way it rotates.
The telescope, during an observation, is resting on four of these feet, which are resting on this concrete pillar.
After an observation, we want to point to a different point, north, south, east and west, so the telescope 100-tonne structure is, as you can see, getting an inch off this concrete.
Supported just by? It's supported by 8 of these airbags, 20lbs per square inch.
Wow! Like a little hovercraft.
Put your hand here, you can feel the air coming out.
You really can! So the telescope, during the night, is operated by the telescope operator from the control room.
It moves round this concrete pillar, the computer tells the telescope structure when it's at the right compass point and then the air is cut off and the telescope comes back down.
This foot comes back down.
How quickly can you move from one object to another? That's always crucial.
Well, the design was just a few minutes, so we don't lose very much time.
The telescope specialises not in taking images, but in using an instrument called a spectrograph.
This splits the light from objects into their constituent colours, telling us what stars and other objects are made of.
David took me to the Observatory's new visitor centre, which uses light from the sun to explain what the spectrograph does.
We're producing an image of the sun and the image is projected from a telescope on the roof of a building.
From the image of the sun, a little slot of light is fed back to a diffraction grating - think of it as a prism - it spreads the light out into a spectrum, a rainbow of colours, and that's what you see projected.
As well as the rainbow from violet through to red, I can see dark lines in the spectrum.
They're important.
We call these Fraunhofer or absorption lines and they are produced by atoms of different chemical elements in the atmosphere of the sun absorbing some of the light.
So, from those lines, we can trace out which elements are present, which are not and determine also the amount of those elements, things like the temperature and pressure and the velocity flows in the atmosphere of the sun.
With the power of the Hobby-Eberly's giant mirror behind them, astronomers have used a spectrograph to study stars sprinkled throughout the galaxy.
So what can the Hobby-Eberly Telescope tell us about stars in our galaxy? Because of the large aperture, the telescope can look at quite faint stars, and we have the high-resolution spectrograph in the basement, so one can determine whether there's a correlation between the metal content, as we say in astronomy, and the motions of the stars, an ultimate lead to clues as to how the galaxy was assembled.
In a star like the Sun, the metals make up less than 2% of the mass of the star.
And they come from previous generations? They come from previous generations of stars by nuclear reactions inside the hot interiors of stars.
There are then processes, usually explosions, that get those elements out into the interstellar medium and new stars form containing these metals, or contaminants.
I know you've looked for some of the metal-poor stars, those which are relatively pristine.
Why are they special? Because they were formed early on.
The search right now is to find the most metal-poor stars.
There have been recent discoveries where the metal content is one part in 10 to the 5th.
That's one part in 100,000? Correct.
And those stars, possibly, formed from gas that was contaminated only by the very first generation of stars to form from the Big Bang, and they were very special stars because they only contained hydrogen and helium.
I've been to many observatories around the world, but I've never seen anything quite like the Hobby-Eberly Telescope.
It may only be able to see a fraction of the sky, but the ingenuity of its design is hard to beat.
Every telescope, every observatory has its own story, from the new technology of the Hobby-Eberly behind me to the amazing legacy of Kitt Peak, with a new generation of giant telescopes already under construction, I'm sure the most amazing stories are still to be written.
And that takes us on to the future.
Where do you think the future lies? Well, the future does lie with segmented mirror telescopes.
Three groups are planning larger telescopes than the Hobby-Eberly and the Keck Telescopes and all of them involve segmented mirrors.
So, starting with the Thirty Metre Telescope - this is a collaboration between Caltech, the University of California, Canada and Japan and the segments themselves - there will be 490 of them.
So a telescope of that aperture is really very, very powerful.
One of the driving forces is to study galaxies at the very edge of the universe, perhaps the first generation of galaxies to switch on, when the universe is only 3-4% of its present age.
What about the atmosphere? We have to get rid of the atmosphere, because it blurs the signal.
Fortunately, adaptive optics has made tremendous progress over the last 10 years.
It's quite challenging to correct for the blurring over the big aperture like a 30-metre diameter.
How exactly do you do it? The way it works is, you shine a sodium laser beam into the sky along the direction of the object you're interested in observing, and this reflects off sodium atoms high in the atmosphere.
Which are there already? Which are there already, and they create a spot of light which is effectively an artificial star.
We monitor the signal from that artificial star and correct for the blurring using a deformable mirror, a small mirror made of many components, each of which can be moved independently.
How many corrections per second? It's several corrections per second, and these deformable mirrors have several hundred individual components.
So the technology is demanding, but the progress has been so great that we're now optimistic it can be applied to these larger telescopes.
So the other telescopes are the European Extremely Large Telescope - this is a 42-metre telescope.
That is really a balance between the amount of money that ESO thinks it can raise for a telescope of this aperture and the desire to have even better performance than the Thirty Metre Telescope.
The final project, which is quite exciting, is the Giant Magellan Telescope.
So it's an exciting time, driven by fundamental scientific questions, such as imaging extrasolar planets, looking at the earliest objects in the universe and, of course, studying cosmology and dark matter and the fundamental questions of the origin of life and the nature of the universe that we live in.
Well, Richard, why the quest for even bigger telescopes? It never ends, Patrick.
George Ellery Hale once said, "Light is falling on the Earth from all over the sky "and all we can do is collect the bit that lands on 100 inches across.
" He was driven to build bigger and bigger telescopes to learn more about the universe - the quest never ends.
The technology enables us to do it.
It's a very exciting future.
Richard, thank you very much.
Thank you.
We began the series way back in April 1957 and look how much has happened since then.
Despite all the electronics, visual photography is still used for some branches of research.
David Malin, who came to Siding Spring as a photographer, spends his observing time in a cage at the fine focus.
The official name of the observatory is El Observatorio del Roque de los Muchachos.
I'm afraid my Spanish accent isn't very good, but here are Los Muchachos, the two boys.
I'm sure there is a local legend about them, but no-one seems to know it! There is the moon.
I can see it for the moment.
No, it's gone again.
It's gone.
Infuriating.
There's nothing one can do.
The heart of any telescope is its mirror, and here we have the 4-metre or 158-inch mirror of the main telescope on Cerro Tololo.
It really is enormous.
It's two foot thick, and it weighs 15 tonnes.
We're clouded out here.
There is sometimes wait a moment There's a break over there - can you see? I can't see anything in it, though.
No.
This neat and efficient-looking dome contains a 10" reflecting telescope.
Just to make sure we know where we are, the latitude and longitude's on the door.
The Royal Greenwich Observatory gave it to me to pinpoint my position if I sent in any observations.
Do you find that the dome's easy to turn? Once you get it going, Patrick, it's quite easy.
See? Just you have a try.
Yes Oh, that's pretty easy.
There's no difficulty there.
There's still a lot of drifting cloud up there and we can't tell if it'll be obscured at the critical moment.
You won't see Vega looking large, because no telescope will show It's gone, Patrick.
Has it gone? Oh, no! Just as I got it on the cross wires, it blacked right out.
How typical! Nothing we can do.
The next morning, there was a 70mph gale, and when I arrived the wind was really tremendous.
It was just as much as I could do to open the door to get inside the Great Dome.
Astronomy is unlike anything else, and one can give as much time to it as one wants.
You can get a tremendous amount of enjoyment and if you do useful work too, so much the better.
Good night.
Good night.
And so, from Brighton, where the sky is now completely overcast, good night.
Good night.
Well, I think you'll agree, it's a wonderful story.
We've come so far in the last 400 years, from the tiny telescopes of Galileo's time through to the huge telescopes now.
We can look back into the depths of the universe.
It's a story well worth telling.
I hope you've enjoyed our look back at the history of the telescope.