Professor Ben Gascoigne (1915-2010), astronomer

Professor Ben Gascoigne. Interview sponsored by 100 Years of Australian Science (National Council for the Centenary of Federation).

Sidney Charles Bartholomew Gascoigne, known as Ben, earned a BSc at the University College of Auckland (now the University of Auckland). A travelling scholarship took him to the University of Bristol, where he received his PhD.

In 1941 Gascoigne came to Australia to join a team working in optical munitions at the Commonwealth Solar Observatory, Mount Stromlo (near Canberra). After the war he continued at Mount Stromlo, conducting astronomical research. He had a particular interest in stellar evolution, the scale used to measure distance and faint star photometry.

Among Gascoigne's most important achievements was his work in establishing the Anglo-Australian Telescope at Siding Spring, New South Wales. Commissioned in 1974, the 150-inch telescope is part of the Anglo-Australian Observatory. He was honoured with an Order of Australia in 1996 for his service to Australian astronomy.

Interviewed by Professor Bob Crompton in 2000.



Professor Gascoigne is a distinguished astronomer, well known internationally for his pioneering work on Cepheid variables and star clusters, and for his central role in the establishment of the Anglo-Australian Telescope.

Born in New Zealand in 1915, he took his first degrees at the University College of Auckland, now the University of Auckland, where he was awarded a travelling scholarship which took him to the University of Bristol. A gifted mathematician, he first saw his future as an academic mathematician, but later became attracted to theoretical physics. In Bristol, circumstances changed his interest yet again, this time to optical physics.

Although slowly converging on his eventual career path, it was not until he had given some years of wartime service to optical munitions, first in New Zealand and then at Mount Stromlo, in Australia, that Ben Gascoigne finally embarked on astronomy.

During this interview he will describe his early years and the circuitous path that eventually led to astronomy and his distinguished contributions to it. Among the most important of his achievements was his work in specifying and commissioning the 150-inch telescope at Siding Spring, the Anglo-Australian Telescope. No-one is better placed to detail the history of that project, about which he has written extensively.

Now an Emeritus Professor of the ANU, Professor Gascoigne was honoured with an Order of Australia in 1996. He is an Honorary Fellow of the Astronomical Society of Australia, and is justifiably proud to be the first Australian to be elected an Associate of the Royal Astronomical Society. He is also the first person to be elected as an Honorary Member of the Optical Society of Australia.

History was one of Professor Gascoigne's early passions, and in his retirement he has continued to write extensively on the history of Australian astronomy. He has also devoted much of his time to assisting his late wife, the distinguished artist Rosalie Gascoigne, including cataloguing her extensive works of art. This interview will conclude with some reminiscences of their life together.

New Zealand family tales

Ben, may we begin with some family history? I understand you are a New Zealander by birth.

Yes. My mother's forebears came out to New Zealand by ship in 1840. Later, in 1870, my father's parents were passengers on the  Piako; perhaps they met on board. Anyway, they were married in New Zealand.

I believe that the 1840 ship was greeted by Maori warships.

Well, with some other ships it went to Wellington, which was just pristine country with no buildings there at all, and when they anchored off the shore they were greeted by three Maori canoes – their crews, in full wartime regalia and chanting their hakas and so forth, paddled out and circled around the ships. Perhaps because a small advance party of Edward Gibbon Wakefield's company had been there before, the welcome was friendly, but I don't suppose the Europeans could have been certain of that for some little time!

The voyage of the  Piako  too has a story. It was one of the first iron-built ships, which was just as well because just off the coast of South America the luggage caught fire. Luckily, the hull and the decks didn't catch, but it was very alarming and everyone had to abandon ship. Some other ships picked them up and no-one was lost, but they couldn't land at the nearest town – Pernambuco, also known as Recife – because there was a cholera epidemic on, with about 300 people dying each day. Instead, they established a camp on an island about nine miles up a nearby river, where food was taken up to them more or less daily from one of the towns. The ship had been saved, however, by the resourcefulness of the captain, who sank the ship to put the fire out and then refloated it. He sent back to London for a set of interior fittings to replace the ones that had been lost in the fire, and nine weeks later they all set off again and landed in Lyttelton.

Not many families would start off in a new country that way. Your father began his professional life as a teacher, didn't he?

Yes, he did. He taught at three or four schools, one of which was in Levin, a small town south of Palmerston North; at a Maori boys' school, Te Aute College (a very famous Rugby school); and at Napier Boys' High School. Levin was where my mother had been born and raised, and my parents were married in Levin just at the outbreak of World War I before going to live in Napier, where I was born in November 1915. Later, my father's brother-in-law persuaded him to join his wholesale dealership in hardware goods such as motor machine parts and bicycles, so we moved to Palmerston North for about five years. Then, when I was about eight, my father got a similar, better post in Auckland and so we went up there.

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Through school to university, via hard work and keenness

Were you in Auckland right through your primary, secondary and tertiary education?

Yes, until I left for Bristol.

Where did you do your secondary schooling?

At Auckland Grammar, a big school of 900-odd boys. It had the name for being the best academic school in the country, so I was lucky. The four forms – 3rd, 4th, 5th and 6th – were divided into sub-forms such as 3A, 3B and 3C. I was in the A forms all the way up because right from my early boyhood I was a clever one, the pride of the family.

I didn't go straight from 5A to 6A, though. Being in the top few of 5A I should have done so, but I was beguiled by the writings of John Galsworthy, H.G. Wells, J.B. Priestley and co., and I didn't do all that well in the end-of-year examinations. To my great indignation I found myself in 6B instead. 6A was the scholarship form, so I determined to get a university entrance scholarship from where I was in 6B, which I don't think had been done before. I worked like fury, and a few weeks later I was restored to my 'rightful' place in 6A. That was a useful lesson and I didn't stop working in that way, so I came second for the year in 6A. In fact, I also got a scholarship a year early. I took that lesson to heart, deciding that if I worked hard enough I could do almost anything. That has stood me in good stead.

And so you went to university at the then Auckland University College. How did you choose which subjects to do there?

Well, I wasn't any good at the languages, French and Latin. In my scholarship year I dropped Latin and took history instead, and I was very keen on history all the way through. When I went up to university, I had to choose essentially between doing a BA in history and doing a BSc in mathematics and associated subjects. Because I had a bad stammer all through the early part of my life, I thought it was going to be easier to get a job if I had a science degree, and so I opted for maths, with chemistry. I had to have one more subject, so I chose physics. I hadn't done physics at school but I found I was a dab hand at it – I sailed to the top of the class and remained there all through university. I was very keen on both physics and maths.

A mistaken scholarship attempt leads to a lucky choice

You have told me that one of the people who were very influential in your life was your professor of mathematics.

Yes, H.G. Forder. In fact, there were only two on the staff. The other one was Keith Bullen, who eventually became the applied maths professor in Sydney. He was good, too, but Forder was a brilliant and inspiring teacher, especially for people who were keen on mathematics. The syllabus was undemanding, and having plenty of time on my hands I ranged far and wide beyond the syllabus. Whittaker and Watson was my chosen pasture in those days. One of the chapters was on theta functions – functions of two variables – which I enjoyed, working out all the examples. But it was years before I met them again, when Rodney Baxter gave me the reprint in which they occurred, and I thought, 'Ah! I know what those are.'

At that stage you were quite enthralled with quantum mechanics too, weren't you? That would have been in its very early days.

Yes. I must have read Sommerfeld's book; there weren't many books on it at that time. I got particularly fascinated later by the Mott and Massey book on atomic collisions, but we'll come to that.

I think your choice of subjects almost caused you to miss out entirely on a travelling scholarship. Why was that?

There were only two travelling scholarships, one in arts and one in science. Because I was taking a degree in science, taking my honours in mathematics, in my science scholarship application I put down maths as my subject. But it turned out that for the purposes of the award of these scholarships, maths counted as an arts subject. I should have entered for the arts scholarship, and so I missed out – even though they had pencilled my name in, I heard. I was very upset, but luckily I was able to get a bit of money for another go. I applied for a second honours degree, in physics, and this time I got a First all right and a Michael Hyatt Baker scholarship.

The scholarship was named for a young man from Bristol who had been travelling the world but was killed in the Napier earthquake of 1928. His parents set up the scholarship in his memory, for study at the University of Bristol, so I found myself going to Bristol instead of Cambridge, where I had always set my heart on going to do mathematics. But in the long run Bristol was a lucky choice for me.

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The pleasure of solving a long-standing optical physics problem

The scholarship placed no restriction at all on which subject I did, but at that time there was no effective maths at Bristol and so for me it had to be physics. Mott was there then, and when he asked me what I wanted to do, I said how fascinated I had been by his book. He said, 'Oh no, that's long past. We're into the theory of metals now. You can come along to the class and see how you get on.' But when I went along I found the metal theory didn't appeal to me at all – it was about semiconductors, which I was totally unaware of, and lattice dislocations and things like that – and I saw that he had 17 PhD students who would be my rivals. I thought, 'Even if I do get a PhD out of this, I'm never going to make it against this lot.' So I went back to Professor Tyndall and asked if anything else was available.

Bristol was very much a place for experimental physics, but I was still very much a theorist, with no practical physics at all. The professor in Auckland used to wince when I walked past the cupboard in which the good instruments were kept! Anyway, it was agreed that I could get into work in astronomy, in which I was interested, by way of an astronomical optical problem.

Didn't that PhD subject bring you your first research success?

Yes. At first I was most unhappy to find myself in such a dry subject as geometrical optics, which was then a very out-of-the-way and despised subject. There were two people well into doing optics at Bristol, however, and later the department became quite celebrated as the Bristol School of Optics. One of those people was Dr C.R. Burch, an extraordinary man, a master of physics of all types except quantum physics. He was interested in making big mirrors, in particular, and he had made one for University College, London, using a method of his own to test it. I think it was an 18-inch.

Since about 1850 the Foucault knife-edge test has been familiar to everybody who makes big mirrors, but there wasn't any diffraction theory of it. Burch had a particular problem that he thought might be explained by such a theory, and so he asked me if I would like to have a go. Now, the great Lord Rayleigh had tried this but had never got beyond the perfect mirror, and the great Dutch optician, Zernike, had been able to solve it only for very small errors on the surface of the mirror, so small that they really didn't matter in practice. To my great surprise I came up with an exact solution of the knife-edge problem, and I was able to show Burch's surmise was correct. I was very pleased that that turned out well.

Burch was a practical man who worked with his hands a lot – making his ultraviolet microscopes, reflecting microscopes – and I picked up many odds and ends about optics from him. He showed me all sorts of ways of testing mirrors and many optical devices. I think those things, which came by the way, were just as important as my thesis.

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An unscheduled but rewarding return to New Zealand

Then it was back to New Zealand and to Rosalie. Perhaps you could digress there and say how you first met her.

We had been to the same primary school, where I was two years ahead of her. Although I met her socially, because we lived in the same suburb, nothing much came of that until she went up to university (two years after me) and we began to see each other again – especially in my fifth year, when I was doing that unexpected second honours degree in physics. I became quite decided that she was the girl I wanted to marry, but then I went off to England. The war broke out when I was about halfway through my time in Bristol, and thinking that if I stayed in England I would never be able to get back and might never see her again, I put in for the one last ship that was leaving. Although we left just before the Battle of Britain, on the whole journey home we never heard a word about it, and to find out about it when I landed in Sydney was a great surprise.

On the ship home I fell in with an abstract artist, Carl Plate, who was going back to Sydney. After a crash course he gave me in abstract art all the way home, I finished up very keen on abstract art and the sort of art that Carl did. Although I went back to Auckland, of course, through him I had become very much aware of the existence of art and of art galleries. I had met a few artists and I knew that there was an art community, into which I was able to introduce Rosalie when we got married.

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Optical munitions, with some bridge games on the side

In New Zealand, this being at the beginning of the war, your first job was in optical munitions. Is that right?

Yes. The small physics department, like physics departments all over the place at that time, was enlisted to help with the war effort, in particular with military optics – mostly gun sights, rangefinders, binoculars and so on. My first job was a practical one, making a little gun sight for a trench mortar. It was a single piece of glass, only about two inches long: when you looked in one end you saw a V projected against the landscape. Actually, it was quite effective. And so I had to organise a little workshop at the railways workshops, out of Auckland, with a staff of four. Oh, this was fascinating. I could see what was going on in the main workshops; they'd demonstrate their big steam hammers to me and so forth – my first contact with industry.

You didn't stay very long, Ben. I understand that you wrote to Woolley, who was at Mount Stromlo doing work similar to what you were doing in New Zealand.

Yes. As a member of a team working on optical munitions I was privy to various reports that came in, and I read one from the then Commonwealth Solar Observatory which described their entry into the optical munitions business. This was on a far bigger scale than anything I could have got into in New Zealand, and so I wrote to Woolley with a sketch of what I had done and asked if there would be a position for me. He wrote back very promptly and enthusiastically because he had heard that I had been working with Dr Burch, 'who of course was well known in the astronomical profession'. He offered me a job, and as soon I could get a release, over I went. I wasn't yet married to Rosalie, not on the sort of pay I was getting in New Zealand. But the Mount Stromlo salary was about £350, which was not bad in those days.

My introduction to Canberra and to Woolley was interesting. The little old train meandered through the landscape and past stations like Mount Fairy and Bungendore, and eventually pulled up at what I presumed was Canberra because everybody got out. This tall figure that I was going to know so well came striding across: 'I'm Woolley. Do you play bridge?' I said, 'Well yes, I do.' 'Contract?' And I was off to a good start.

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Settling in among Mount Stromlo's characters

You had some very interesting experiences in those optical workshops at Stromlo, both scientifically and also because of the people you met.

I did. We were the one place in Australia which could build a whole instrument from the initial layout and optical design through to the optical and mechanical manufacture, the assembly and testing. We made one-offs to see how they would go, and things for the Army Inventions Directorate, for example. Also occasional small batches of 20 or 50. As a training ground for a budding optical astronomer it would have been hard to beat. When I began there, it was not clear whether I was to be an experimentalist or a theorist; certainly I began as a designer, but I moved on. I got some incredible experience there – even if none of it was in theory at all. And I finished up quite practical, especially with a screwdriver.

It was one of your first experiences of multiculturalism, wasn't it?

Yes. Woolley's charter was to make optical fire control instruments such as sighting telescopes and artillery directors, gun sights and rangefinders, not only the mechanical parts but the optical parts too. Very few people in Australia had any background in that, but at about that time the notorious ship  Dunera  arrived with a load of refugees – mostly, but not entirely, Jewish – who had fled from Europe to England, only to be shipped off to Australia when the war broke out. Thinking that some of them might well have some optical skills, Woolley went up to their camp at Hay, interviewed a number of them and hired about six for Stromlo.

We were living up on the mountain at that time, in a kind of barracks for single men which could house these European people as well as about four or so of us Australians and New Zealanders. Stromlo was a very isolated place, with little transport into town and certainly no motor transport. Because of petrol rationing you got enough petrol for only about two trips a month, so we all had bicycles. Living and working in such close quarters we got to know each other very well, and this was a great success. We all made good friends – some of mine have lasted to this day – and it was a very educational experience because of the odd hint or remark about problems in Europe. They seldom spoke of their experiences in any detail, but we were all aware of them.

On the weekends we would go for picnics or walks down to the Murrumbidgee, or go on our bicycles over into the ranges, but the refugees were confined to the ACT and when we rode out to the border between the ACT and New South Wales they would get down on their hands and knees, creep out and reach a hand over the border, just to touch foreign soil! They were funny, a very witty lot on the whole. It was a great experience.

Who else can you tell us about?

Well, I began work up on Stromlo designing an anti-aircraft gun sight. After I finished this design, the need arose for a department for testing and inspecting pieces, made in part by the optical shop and in part by the machine shop. This grew into an assembly place for whole telescopes, in which I found myself second-in-command to Cla Allen, a celebrated solar physicist who was on the permanent staff there. We recruited an incredible range of people from all sites and all ranks of life. The oldest one, Herb Willetts, was about 75. He had been the chief engineer on the Victorian Railways and insisted on doing his bit for the war by sweeping out the machine shop every day. He was a great old boy and we really respected him. Allen left for other duties within a few months, and I was put in charge.

Another unusual person was a man from Scotland who had worked with the firm who built the Barr and Stroud rangefinder, so he was handy. But he wasn't very energetic. He was a bit of what we used to call a 'pointer' when I was young. He would say, 'When you're walking from one section to another, always carry a piece of paper in your hand, because that makes it look as if you're going on purpose. A slide rule isn't a bad idea, either.' Little comments like that really upset us, though.

And through Unity Cunningham, a member of the Cunningham family, from Lanyon, near Tharwa, we were once or twice invited to have a Sunday afternoon cup of tea with one of her distant relatives, Sir Robert Garran [Australia's first Solicitor-General]. She was looking after him in his old age. He was a grand old boy, knitting camouflage netting and things like that while he sat by the fire. He wouldn't let a minute go by; he was determined to do something towards the war effort.

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The Commonwealth Time Service

How did it become your task to set up the Commonwealth Time Service at Stromlo?

That had been run from the Melbourne Observatory until about '42, when the then director, Dr Baldwin, retired. Woolley knew about time services, having had charge of the one at Greenwich, and was keen for us to take it over. Part of the reason was that the Army Engineers needed good time for longitude determinations. I had that job for a couple of years, and it was a nice one. We built a little transit telescope for measuring the instant at which the standard time stars crossed the meridian, this was our primary data. We collaborated too with the Post Master General's laboratories and their quartz clocks.

Would you tell us your story about the transit instrument?

Woolley said we would need to build our own, and we did so, using as a base the frame in which an old surveying instrument had sat. Kurt Gottlieb (our engineer from Czechoslovakia) and I would make drawings and then march in to show them to Woolley. He would look at them, puff away at his pipe and say, 'Very good, carry on.' We'd go back in a couple of weeks and report progress, same response. And then one day we marched in and said, 'Well, we think we've finished. Would you like to come out tonight and try it?' It worked perfectly, but he was furious that we had completed it all 'without consulting him'! We'd been consulting him all right but he'd never taken any notice. I'm sure he made a good story of it afterwards, though.

Actually, making this transit telescope after all our experience in military optics was a breeze. We'd made military instruments that were far more demanding, except that some components had to be really accurately machined. But the place was up to that.

Woolley's Stromlo telescopes

Woolley had come out initially to establish stellar astronomy in Australia. What was taking place at Mount Stromlo between the end of the war and when his era there finished in about 1957?

We had to start from a long way down, because there wasn't much to begin with. The telescopes were all old and hadn't been used for years. Everything had to be overhauled, reconditioned and refurbished. The youngest and biggest of our telescopes, the 30-inch reflector, only went back to about 1930 but it was rather an amateur telescope which had been given to us by the then President of the Royal Astronomical Society, an engineer named Reynolds. It was a glass reflector, chemically silvered, but we were able to have it aluminised fairly soon when Arthur Hogg built a tank in which we could aluminise pieces as large as that.

We also had the old 50-inch, which we had inherited as the 48-inch Great Melbourne Telescope. Melbourne had acquired it in about 1868, when it was the biggest working telescope in the world, but its use was very limited. In particular, it couldn't be used for photography, which began in about 1880, and so it sank into disuse. We bought it as scrap at the end of the war and although we could use quite a bit of the mounting we really had to rebuild the whole thing, putting in new optics and new controls. It all took quite some time.

Tell us the later story about its speculum mirror.

We had inherited two mirrors with our telescope, both of the copper-tin alloy speculum. Speculum had the problem that while it could take a high polish, it tarnished rather quickly and had to be repolished. Two mirrors were provided so that when the one in use became tarnished it could be swapped for the other, ready polished. The first mirror lasted a surprisingly long time, but the second suffered an unfortunate event: in the optical shop one day someone saw it teetering on edge, and it fell to the floor and smashed irredeemably. Speculum is notoriously brittle. Disaster! Knowing that Woolley had a violent temper, our two optical technicians wondered how they could give him news of this without losing their jobs. Eventually they plucked up courage, just before knocking-off time, and told him the bad news. But to their surprise and relief he just leant back and laughed his head off. The fragments of tin and copper were sold for more than we had paid the Victorian government for the whole telescope (it had been purchased as scrap).

Before long, though, in about 1956, we got a 74-inch. Woolley had approached the prime minister, Chifley, about this fairly soon after the war, but came away rueful about getting approval for it. He said Chifley agreed to the 74-inch so readily that he thought he could have got a 100-inch without any trouble at all! Building it took a long time and it wasn't finally erected until after Woolley left. We had to learn how to use it because no-one on the staff had never used a big telescope – we had hardly even seen one – and then the primary mirror turned out to be astigmatic and had to go back, being replaced for a while.

It hadn't been tested properly, but I must say that it is all too easy for big mirrors to go astigmatic if they are not held properly while they are being figured. Also, if they are tested along a horizontal path where the air can layer, with hot air on top and cold air below, this can simulate the effect of astigmatism – and by the time you have polished it out, the mirror really is astigmatic.

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Strong advocacy and a satisfying outcome

I understand that in that period between the end of the war and Woolley's departure you had Colin Gum, one of your very distinguished scholars, working with you.

Yes, I did. Cla Allen was his original supervisor, but then Cla left to take up a position in England and so I inherited Colin. The topic Cla had put him onto was to look for H-alpha regions, where the hydrogen in between stars is illuminated by very hot stars with lots of ultraviolet to excite the red H-alpha line. That turned out to have great importance, because it had been found in other galaxies that these regions lie preferentially along spiral arms and so if you could work out how far away they were you would have a good chance of tracing the spiral arm in our Galaxy. This in fact is exactly what happened, but it wasn't known at the time when Colin began his work.

Colin discovered about 60 or 80 H-alpha regions in the southern part of the sky, which hadn't been surveyed for this at all. Among these was the great Gum Nebula – since named after him – in the constellation Vela. It turned out to be the remnant of a supernova which had gone off only a few hundred years before, and all these pieces were still expanding. An H-alpha picture of this remnant is huge, spectacular.

There was a very exciting moment when it was realised that while Colin was tracking one arm of the nebula, someone in America was tracking the other arm. But by then Colin's thesis had been submitted. What happened then?

Well, after he had written his thesis he had to go into hospital for medical treatment. During the year he was away, I had to supply all the references, and found that looking them up was a tedious and difficult job – I finished up knowing an awful lot about H-alpha regions myself! When Colin put his thesis in, the two examiners were Woolley and a Professor Plaskett at Oxford. Woolley came in one day and said, 'Gum has failed his PhD.' I think Plaskett was the snag, because he couldn't have known anything about the subject, but I don't think Woolley read the thesis properly, anyway. I don't want to sound too critical of Woolley, because he did a great deal for the Observatory, but he did have these idiosyncrasies. I was most indignant and very distressed that Colin had failed, because I thought he was really good. When I told my wife about it, saying that somebody would have to take it up with Woolley, she said, 'Well, you know who it has to be, don't you?' I knew too. Oh dear!

After lunch that day I dragged back up the hill, knowing I had a real job on my hands. Woolley hated having errors pointed out to him. He was a very powerful personality who could get very angry: his face would turn black, and he was very quick with his tongue, with counter-arguments. He would have been an excellent lawyer, I always thought he may have missed his profession. Anyway, I marched in and battled away as best I could until we were interrupted – I was truly thankful for that and went home, the matter quite unresolved. Next day I was back again, batting away, and I thought I made a bit of progress. And on the third day Woolley agreed to appoint a third examiner, Cla Allen, who was by that time in London. And so Colin got his PhD.

From then on, when the staff had little grievances and so forth they wanted to air to Woolley, I was always the elected spokesman! I had established my position.

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The significance of the Magellanic Clouds

At this point I want to take a rather different tack and treat three themes: the Cepheid variables, globular clusters, and your part in the Anglo-Australian Telescope, which you were extremely influential in establishing. To introduce the theme of the Cepheid variables: What is the significance of the Magellanic Clouds, Ben?

They have figured very largely in southern hemisphere astronomy. Not only are they objects of the first importance in themselves, but they are a long way south and can't be seen from the north. The point about the Clouds is that they are by a long way the nearest galaxies outside our own. They are small galaxies – the Large Cloud is about a tenth the mass of our Galaxy. They contain an enormous variety of objects of all types, all at the same distance, which makes it easier to compare them. This is a huge advantage in astronomy, where the distance problem is always with us.

Our Galaxy is a flat, plate-shaped object with quite a dense central nucleus about which it spins. We are about halfway out from the centre, about 25,000 light years. Beyond us it thins out and gets very diffuse, with no well-defined edge – an overall diameter of, say, 100,000 light years. The Large Cloud is 180,000 light years away, the Small Cloud a little further; relatively speaking, they really are quite close neighbours.

You speak as a true astronomer, Ben: a couple of million miles is absolutely nothing to you, is it?

That's right. It's about 10 light-seconds. I must say that the Large Cloud turned out also to be a flat object, on a tilt. You can measure the difference between the near side and the far side of the tilt – as in fact I did, to my great pleasure. It is rotating, in the same way as the Galaxy is rotating. The Large Cloud is not dissimilar in this way but it is quite asymmetric, whereas the Galaxy is pretty regular. But however asymmetric, it is flat. And then Andromeda, the nearest external galaxy, comparable to our own Galaxy – is about 10 times as far away as either the Large Cloud or the Small Cloud.

Is it unusual in the universe to have clouds like this that are not nebulae?

It used to be thought so, but the picture is changing steadily as we go along. There is a great number of small, isolated galaxies now, of all types. The Clouds are exceptional, perhaps, in that they are pretty young. It has turned out that they are younger on the whole than our Galaxy. Others are quite old and are rather like globular clusters blown up. We'll be coming onto that later.

The Clouds are very significant. They are associated with the Galaxy, and it is surmised that in time they will fall into the Galaxy by gravitational attraction and just be absorbed by it. For galaxies to grow by cannibalisation is a process which has been recognised only in recent years – more or less since I stopped doing astronomy – and it is now seen increasingly as fairly common.

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The Cepheids: establishing the astronomical surveyor's baseline

So what are the Cepheid variables, and what is their significance?

The Cepheids are very important in astronomy, especially for estimating the distances of remote objects such as the Andromeda Nebula and indeed the Magellanic Clouds. To get these distances right is the basis of the whole astronomical distance scale. This is, in a way, the surveyor's baseline from which the rest of the universe is measured.

Cepheids are important for this because they are intrinsically bright stars – among the brightest stars around, many thousands of times brighter than the sun – and they are easily recognisable, because they pulsate and so they vary. They go in and out, in and out, and as they do, their light varies by a factor of two or three, which can be picked up a very long way away. Even in a faint star you can see if it is varying by that much. The periods of Cepheids range from about three days up to 30 days, and a 30-day Cepheid will be about 10 times as bright as a three-day Cepheid. This makes them very attractive to theorists, too, who like playing around with information like that. What also makes Cepheids so useful is that you can determine how bright the ones in the Galaxy are, because you know their distances from other arguments – which we haven't got time to go into here but are good arguments.

The problem which I had been thinking of was measuring colours of the Cepheids in the Large Cloud. The Magellanic Clouds had been the province of Harvard Observatory for the whole of the century. They can't be seen from the northern hemisphere, but Harvard had set up an observatory in Peru (later in South Africa). Harvard began work on Cepheids in about 1908, discovering lots of them in the Large Cloud, and that is when they discovered the famous period-luminosity law. But Harvard measured them only in blue light. They had never measured colours. Besides, the Harvard data that looked so good from 1950 were obtained by methods that were okay in 1910 but hadn't changed their methods at all, and they just weren't up to scratch. It wasn't going to be hard to improve on the Harvard observations.

When you are comparing objects at different distances, the inverse square law holds. That is to say, if you shift a lamp to twice as far away as it was, it is then only a quarter as bright. If you shift it to three times as far away, it is only a ninth as bright, and so on. But if you know the candle-power of the lamp, its output in watts, you can work out how far away it is. Well, that is the way Cepheids work. We see all these Cepheids in the Magellanic Clouds, we know their period so we can correct for the period-luminosity law, and we know how bright they are, therefore we know how far away the Magellanic Clouds are.

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Cepheid colours, galaxy dust and a triumphant insight

However, there is one major complication. There is dust within galaxies, though there is very much less between galaxies. Certainly within our flat Galaxy there are not only stars and a fair amount of gaseous hydrogen, but also a lot of dust. It is a very visible component of the Galaxy. The Southern Coalsack, well-known in the night sky as a big black hole in the Milky Way, does not represent an absence of stars in that direction, it is rather a cloud of dust obscuring the stars beyond it. The effect of this dust is to make your lamp look fainter, and before you can use it as an accurate distance indicator you must work out how much dust there is between you and it.

This is made possible because dust has another property: not only does it make your light look fainter, it also makes it look redder. If you can measure the colour of a star and it appears redder than you know it really is, you can use the amount by which it has been reddened to correct for the absorption by the dust. Measuring the colours of Cepheids is therefore very important. The question of their intrinsic colours – what were the colours of unreddened Cepheids – worried astronomers for a long time. Although they knew the distances of the ones in the Galaxy, they didn't know how much dust there was.

Just as I was wondering how best to tackle this, two Americans from the famous Lick Observatory turned up – Gerry Kron and Olin Eggen (Eggen later became the director of the Mount Stromlo Observatory). Gerry was an electronic instrumentalist, a type then new in astronomy. He was astronomy's leading expert with photoelectric cells, and in particular he had brought along some recently-developed multiplier cells, he knew just how good they were. His own program was to measure the colours of all the red dwarfs in the southern part of the sky. He had already measured all those in the north, but some of the most interesting ones are in the south and he wanted to complete the sample.

He thought he would do this on the 30-inch, and since it would have been a two-man job he asked if I would like to team up with him. He said, 'We can measure my stars from May till August, say, and then we can measure yours. But don't do yours with photography. One of my photoelectric cells should just about handle this.' The stars I wanted to measure were up to that time the faintest which anybody had measured with a photocell, and the trick was going to be to pick them out, to recognise them, in the crowded fields of the Magellanic stars. If you have a map showing 100 stars, and you know one of them is a Cepheid, how do you find it in a telescope?

I really didn't think I would be able to do this, so I used to go up and practise on part-cloudy nights when nobody wanted the telescope. I found it wasn't as hard to do as I would have thought. You hop from star to star and then eventually, 'There it is, for sure.' And so we teamed up and went in to Woolley to ask for some time on the 30-inch. He said, 'Well, you can have the next nine months all to yourselves' – this is on the biggest telescope in the place! – 'but then you, Gascoigne, get no more time for a year.' It was the best bargain I ever struck in my life. Gerry and I got to work doing his red dwarfs in the winter, and the Magellanic Cloud Cepheids in the spring. We could measure them all right, and they turned out to be astonishingly blue, much bluer than the ones in the Galaxy. It was really hard to believe that the ones in the Galaxy were reddened as much as all that, but we pressed on regardless. I did most of the analysis, and after quite a while I thought, 'Let's assume that the ones in the Galaxy are the same colours, are as blue, as the ones in the Clouds' – instead of being yellowish, as they seemed to us – 'and see what happens.' And that was the way to go.

Are the ones in our Galaxy more red-shifted than the ones in the Magellanic Cloud simply because we are looking through a relatively small distance of dust to get to the Magellanic Cloud?

Yes. The galactic Cepheids are in the galactic plane, while the Magellanic Cepheids are well above it. If you assumed the Galactic Cepheids did have the same colours as those in the Clouds, and if you assumed that we knew their distances correctly, it followed from our work that they were four times as bright as had previously been thought. This was startling, because it meant that the Magellanic Clouds were twice as far away as was previously thought, and if then the baseline is twice as long, the size of the universe is doubled. This was not altogether a new result. Walter Baade had proposed the same thing a year or so previously, but on quite different evidence and talking about the Andromeda Nebula, whereas we were talking about the Magellanic Clouds. At least we were able to give him good solid confirmation, and also greatly to strengthen the position of the Magellanic Clouds as distance indicators. By now we knew enough about them to be pretty confident about the answers they gave.

When suddenly all this dropped into place, after I had been working away at it for quite a while, measuring more Cepheids in our own Galaxy and some in the Large Cloud, the feeling of triumph, the great feeling that I had really done something, was wonderful. I had joined the professional astronomers. Not only that, but I truly understood a problem, a proper problem.

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Astronomical anecdotes

I think you have another story to illustrate such a feeling of achievement.

Yes. It is about Ed Purcell, a Harvard astronomer who got a Nobel Prize for predicting the existence of the 21-centimetre hydrogen line in the Galaxy. On one occasion, after he had given us a talk at Mount Stromlo, we were standing around outside and chatting to him. This was the time when Hanbury Brown was putting up his interferometer at Narrabri, but nobody could understand the Hanbury Brown experiment. (I remember even Oliphant coming up one day to ask me, 'Ben, can you explain the Hanbury Brown experiment to me?' I had to say no, I couldn't. It was most humiliating.) Ed Purcell told us that he had been worrying about the Hanbury Brown experiment for weeks and weeks, and then suddenly one day, when he had just walked inside and sat down on the sofa, he sat bolt upright and said, 'By God! I understand the Hanbury Brown experiment.' He went on to say, 'And on that day I felt I really had achieved something.' And I thought, 'That's the key sentence.' I feel that's a good scientific story: achieving understanding is the essence of what you want to do.

And even if sometimes another person has understood – in this case, Hanbury Brown knew exactly what he was doing – the important thing is your triumph of understanding and really feeling it as your own, isn't it?

Sure, that's true. It can be very hard to master something that seems clear to somebody else. I had several programs on Cepheids and worked on them for about 15 years, and I observed the light curves of about 50 all told.

Another anecdote you have told me concerns the generosity of Kron some years later, after a bushfire at Stromlo which destroyed the shop and a lot of other things.

Yes indeed. That bushfire wiped the workshop out – being impregnated with oil and grease, it went up like a torch. At one point, a cylinder of oxygen which had been in there for oxyacetylene work must have ignited. It exploded with a terrific roar, and came flying out through a double brick wall, with its thick steel walls peeled back by the power of the explosion as if you had peeled a banana.

Woolley had agreed that when Kron left, the workshop would build for me a copy of his photometer (with which we had been working) but once the workshop had gone it was going to take forever to replace it and so Gerry said, 'We'll make you one and send it out.' That was a most handsome gift, for which I was extremely grateful. It made a great deal possible for me. And it was a vote of confidence, which I didn't mind in the least.

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The benefits of Bok's graduate school

We must by now be up to the time when the Commonwealth Observatory became part of the Australian National University, with Bart Bok as the first director under the new regime. Had Bok arrived when all this Cepheid work was going on?

Yes, he arrived just before the end of this work. I took the final paper in to show him.

He was very influential in building a strong graduate school, wasn't he?

That's so. He arrived in March 1957, just as Parliament was voting to have the Observatory transferred to the ANU. That was a great thing for the Observatory. It made us much freer, in that we didn't have to go through governmental channels if we wanted to buy anything. I don't think Bok could ever have conducted the site survey if we had had to get approval for every move we made.

What he was keenest on doing was to build up a graduate school, which he did with great success. He went around universities all over the country, lecturing the third-year undergraduates in physics and telling them what a wonderful thing astronomy was, and how he had all these scholarships available up on Stromlo. His enthusiasm was infectious and we recruited people that way, including some very good ones such as Ron Ekers. He built up the graduate school and in most years we would appoint three or four students for a four-year course – or shorter if you were lucky – so that we usually had a good dozen or 15 of them around.

At that time Radiophysics had been going great guns – they had discovered flares on the sun; John Bolton had been discovering his extragalactic sources; they had done all that work with the hydrogen line and worked out where the spiral arms really lay; and Bernie Mills had made those great catalogues with his first Cross and so forth. They seemed to produce something wonderful every month. We got sick of it, and we wanted more than anything else to overhaul them. Well, we began to do that when Bok turned up, and I have since thought that one thing we had, that Radiophysics didn't have, was the graduate school. There is nothing like a bunch of clever, uninhibited young students to keep their elders and betters on their toes. In fact, Watson-Watt, who was so prominent in radar work in the war, was once asked how the permanent officers in the Air Force got on with the rather unconventional scientific people who were building their radar. He answered that they got on 'in spite of the typical scientific virtues of irreverence and insubordination'. And that's just what we found too: this irreverence and insubordination sure did keep the graduate staff on their toes.

A key day came during a joint symposium for which Radiophysics came down to Canberra early in about 1963, when Bok had been here for a while. During the coffee break after the morning session, Leonard Searle – a very good member of our staff who went on to be director of Mount Wilson – came up to me and asked how we were going. I said I thought we were going very well, to which he replied, 'Yes. I think so too, I'd say we're ahead on points.' That was a great day for me. We had overhauled them at last.

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Globular clusters: what went on when the Galaxy began?

Ben, we must leave the Cepheids now and go on to the second of those themes, clusters. As before, what are they, what is their significance, and what were you aiming to find with them?

I was getting to the point where I couldn't do much more on Cepheids. Once I had done what I knew I wanted to do, that was about the end of it. Also, the 74-inch from Grubb Parsons was just about coming on stream, and I wanted a project for it.

The Magellanic Clouds are very rich in clusters, and like the Cepheids they are all at the same distance. The problem with working on clusters in the Galaxy is that you never know how far away they are. There are three or four other unknowns that you want to work out about a cluster – the size and the helium abundance, the age, things like that – but if you don't know the distance it is ever so much harder.

To get anywhere with the clusters in the Magellanic Clouds you needed the 74-inch. The great Walter Baade once said that when you've got a big telescope, the best problems are always those at the very edge of what your telescope will do. I knew that this was going to be at the very edge of what the 74-inch would do, and so I had a Baade-type project myself.

Essentially, a cluster is just a group of many thousands of stars, relatively confined in the universe, isn't it?

Yes. In fact, I used to think of a cluster like a swarm of bees, which are very much grouped together without anything much around them, and which do tend to move from place to place as a unit.

Let me tell you what you can do with clusters. It's always assumed that they formed out of a primordial cloud of material at more or less the same time, so all the stars in one cluster are the same age that is a great simplification. As to what you can get from a cluster, first of all you can make quite a good determination of what that age is, and secondly you can have a pretty good go at the metal abundance. You find out that old clusters had low metal abundances; young clusters are rich in metals. People talk about globular and open clusters. I am not very interested in open clusters, which are younger, but globular clusters are quite spectacular objects. There's 100-odd known in the Galaxy, and they are about as old as the Galaxy itself.

One of the great clues to how the Galaxy evolved is that something went on that formed all these globular clusters near the beginning but has never done so again. Knowing of all these clusters in the Clouds, I thought I would try to find what went on there. With clusters, the technique is to measure the magnitudes and colours of as many member stars as you can, or of stars which you adjudge to be members. Once you have made the measurements, if you plot the magnitude against the colour you get certain characteristic patterns which tell you the age and things like that. And so I picked out nine or 10 of these clusters.

While Gerry Kron was out with me, when we had a bit of spare time in which we could measure the total magnitude of a relatively big and easy object like a cluster. When we had measured their magnitudes and colours, we found they divided into two of neat groups of red ones and blue ones. I was after the red ones. This was interesting. The blue clusters were young, and it meant that in the clouds, unlike the Galaxy, there were both young and old clusters.

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Cluster measurements: solving the riddle

For this purpose I had to be able to measure very faint stars, and an American astronomer, Harold Johnson, had just developed a very good faint-star photometer which was an improvement on Kron's. (It was about 10 years after Kron's.) This could measure the light from the star and from the adjacent sky at the same time. The March sky is quite bright, and when you are measuring a faint object you are measuring it against an appreciable background which can contribute up to 90 per cent of the total signal. You have to be able to subtract this background out, because all you want is the little bit that is left. The Johnson two-beam photometer enabled you to do this. Reading a description of one, I went in to Bok and I told him it was exactly what I wanted. 'Do you think we can get one?' I asked. Some money had turned up that the Physics School didn't seem to have any use for, extraordinarily enough, and so Bok said, 'Sure. Go right ahead.' Bok was good that way; with some others of the senior staff it would have been much more difficult. So I went ahead and I got the Johnson photometer.

He was certainly an enthusiast, and he could pick a horse, too. You became the international expert on faint-star measurement, didn't you?

I suppose I did. To measure faint stars you take both photographic plates, which go rather deeper than the photocell – you have to have a plate anyway before you can see what's there, because you've got no hope at all with the naked eye – and then measure the plates. Then you can interpolate from measuring the diameters of the images on the plates with the magnitudes of the stars you have measured photoelectrically, and this will give you magnitudes of the program stars. You get blue plates and yellow plates, and the difference between the two gives you the colour of the two.

The first cluster I tried wasn't old at all but about 'intermediate' age – only about 4 billion years old, whereas the really old clusters are, say, 12 billion years old. This was a new kind of cluster, as most of them were. And the ones in the Small Cloud were rather older than the ones in the Large Cloud – something like Small Cloud, 4 billion years; Large Cloud; 2 billion years. The Small Cloud clusters were metal-poorer, with about a quarter as many metals in their envelopes as stars in the Galaxy, whereas the Large Cloud clusters had about half. This is all very interesting. It is grist to the mill of people who work out models of how galaxies evolved from the primordial murk.

That job was a lot of hard work, and I was pleased that it came out as well as it did. It has become a great industry in recent years. A lot of people with the big telescopes, such as the four metres, and the new detectors especially, can do all this much better than I could. But by and large my stuff seems to stand up not too badly.

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Where, oh where, can we site an Anglo-Australian Telescope?

The third of our themes is Siding Spring and the Anglo-Australian Telescope. The tale goes back quite a way, doesn't it, to the necessity for an alternative site to Stromlo, because of interference by lights at night.

Bok saw this problem as soon as he arrived, and he instituted a great search program. We selected high peaks from maps and toured all over – not only this State, but also South Australia and Western Australia – and we finished up with Siding Spring.

I was in the first lot that went up to that part of New South Wales. Harley Wood, the New South Wales government astronomer, was very keen on it. He was a powerful ally because he had good friends in the State public service and they trusted him. We drove to Mount Kaputar, outside Narrabri, and then to Coonabarabran. We had a look at Siding Spring from a distance, but at that time the height was stated to be only 2800 feet and we were looking for something higher. We kept on going, looking at various mountains out of Condobolin and elsewhere, and Siding Spring dropped out of sight.

A couple of years later Ted Dunham, a member of our staff, found out that the height of Siding Spring was actually rather over 4000 feet. He thought we ought to go back for another look, so back we went with a local surveyor's engineer as guide. We had to climb the last bit on foot. Ted had a bad ankle, and I was ahead of him. That made me the first astronomer to set foot on Siding Spring. I liked the look of the place right away, partly because it had such good features for astronomy – for example, the north and west faces had sheer cliffs that were very good for draining away the cold air – and because of its beautiful outlook, on the edge of the national park. It really is a wonderful place to be. So we went back and told Bart that he should put it on the program.

Did you run tests there to see whether it was as suitable as it looked on paper?

Yes, we set up regular testing. Arthur Hogg organised people to camp up there in tents for a week or so at a time. You measure the ordinary meteorological things like cloud cover and wind, but you also test a quality called 'seeing'. That is the extent to which a star image which ought to be very small and pointlike is degraded by atmospheric turbulence. It is a complicated effect which varies greatly, not only between sites but on the one site at different times, and it is very important astronomically. It governs the efficiency of a telescope. If you have a small but clear image you can go much fainter than if the image is blurred.

Eventually the decision was for Siding Spring. Len Huxley, the vice-chancellor of ANU, had a hand in this. He was very proud to see Siding Spring chosen and developed as an astronomical site, and I believe he would have been a whole lot prouder if he were still around, because within 15 years it had become one of the major sites in the world. You see, we got the Anglo-Australian Telescope and the UK Schmidt, and our own 40-inch, and quite a few other, lesser telescopes. That's a lot.

Ordering a 40-inch was one of the first things Bok did when he arrived. I seem to have spent a large part of my life playing around with telescopes, and I got the job of specifying what we wanted and convincing Professor Mark Oliphant that it was the one we ought to have. It was American but he was very keen that we should stay with England. I managed to talk him round, though, and it was erected on Siding Spring in about 1963. That was a very successful telescope.

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Taking the AAT from a gleam in the eye to a 150-inch mirror

That brings us to the AAT itself, Ben. Was it Woolley who first pushed for that?

Indeed yes. I remember being present at conversations between Woolley and Mark Oliphant, who was very keen on building a 200-inch in the Physics workshop. But in view of the amount of engineering that would have been required, that was a hopeless proposition. After Woolley went to England he revived the project and word was sent out to the Academy here to look for support. There was opposition by the biological lobby to such an 'enormous' amount of money going into an optical telescope, and we were told, 'All you astronomers want to do is keep up with the astronomical Joneses.' But all we wanted was to  be  the astronomical Joneses, which in fact we became.

Bok backed the project strongly and helped to persuade the Academy of its value, and Woolley got some money to send a group of four British astronomers out here. They had a look at all possible sites, and at the Parkes dish. Then we drew up a case for the AAT, including, as an example, a suite of four or six programs that astronomers could go out and do right then and there, if only we had a telescope the size of the AAT. (As it happened, by the time the AAT was finished, the sensitivity of detectors and instrumentation had advanced to such a degree that that whole program could have been carried out on the 40-inch.) The proposal was submitted to both the Royal Society and to the Academy, and after a long, involved process it was agreed on in about April '67.

One of the first things was to set up a technical committee – Hermann Wehner, our engineer, and myself from the Australian side; and Professor Roderick Redman, the director of the Cambridge Observatory, and John Pope, the engineer at Greenwich, from the British side. This was a good committee.

We began by touring round to find what to make the mirror of. There were three competing materials: Pyrex, which got ruled out, various kinds of quartz, and Cer-Vit. That is a quartz-like substance but it is different in additives and manufacturing processes, especially the heat treatment after pouring. After a lot of agonising we settled on Cer-Vit. In fact, I remember that we staggered up to our hotel late at night after yet more lengthy discussions, and when I got up in the morning I said, 'Look, I know I haven't had much sleep, but I don't care what you fellows say, I'm settling for Cer-Vit.' 'Oh,' they said, 'that's what we all think too.'

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The Siding Spring telescope materialises

With a choice of sizes, obviously you go as big as you possibly can. What made you go for 150 inches?

Politically, we thought, that was about as much as the market would stand. There's a big difference in price between the 150- and the 200-inch, just in the cost of the mirror blank alone, and we thought we could do as well with 150. In fact, the original proposal was 120, but I argued with Woolley and Bok that at least we ought to go for 150, because then the observer at the prime focus can ride in the cage. You see, the cage has to be big enough to accommodate the observer, regardless of the size of the telescope, and the size of the cage being fixed, it takes much more out of the beam if it's 120-inch than if it's 150. Nowadays, of course, they've got the very elaborate 2dF arrangement which can take the spectra of 400 objects at the one time, that goes in the cage and leaves no room for anyone. Observing from the cage is now quite unusual.

Where did the mirror and the telescope mount come from?

The blank for the mirror was American, but it was figured in England by Grubb Parsons, the great British telescope builders. In fact, they built the whole of the tube assembly. The mount was made by the Japanese, who did all the mechanical tracking mechanism. Mitsubishi did the driving control system. They did a miraculous job.

The computer control system was done here, in house – a big job. It became obvious that the optics and the mounting were first class, but the real  tour de force  was the computer control system. It was the first such example of computer control, and it rocked people that you could move such a big telescope any way you wanted to. Also that you could point and drive it with such incredible accuracy. Paul Wild's Culgoora radioheliograph, with a hard-wired system, was finished in 1966, and in '67 our technical committee decided to go for the computer control system. Actually, it was a leap in the dark, because the computers then available would not have done it. We had to count on bigger ones coming available. On the whole we had good support, including from Fred Hoyle. The British were convinced by the success in England of a computer controlled radiotelescope, but of course the demands of an optical telescope are much greater.

We have had some compliments on the AAT. One was from Glen Haslem, an English radioastronomer, who was so impressed by seeing how accurately it set and drove and all the things you could do with it that he announced, 'Oh, Ben, that telescope's wonderful. It's just like a radiotelescope!' Which to him, at any rate, was high praise. And Virginia Tinsley, a very prominent astronomer, told Robyn Williams during an interview that when the number of references which are made to papers published from each telescope – the impact factor – is added up, we are on top and have been for some time.

I must say this: I worked for several years with the project office – with not only senior engineers but junior ones too, about 24 people all told – and the spirit, the feeling in that office was remarkable. Everybody was absolutely determined that this job was worth the best that they could do. One of the draftsmen actually said, 'This is the best job I'm ever going to have in my life, and I'm going to make the most of it.' I used to think that people building the great Gothic cathedrals might well have been motivated by the same feeling. It wasn't only a good job but it had a noble purpose. It was a wonderful thing to be associated with – the high point in my life.

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Deliverance: a near miss, and a handicap overcome

It is actually very lucky that you are here giving us this interview, because I remember the story of you stepping off into infinity, as it were, when the telescope was being built. Would you tell us about that?

Well, that was lucky. Inside the dome, at the same height as the wheels that the dome runs on, there is an internal catwalk with a tubular safety rail. Before we put up the last section of this rail, it was lying on the floor. I was 'nominally' in charge of the project then – not much in charge because everyone seemed to do what they bloody well wanted! – and so I went around warning everybody, 'Don't forget, don't go wandering around up there tonight.' But while we were taking a plate of the Omega Cen[tauri] cluster, I went outside to the outer catwalk. I must have walked around and along, out one door and in another, and when I came back and felt around for the rail it wasn't there. I just walked right over and dropped 20 feet onto the floor below.

The carriage into which they lower the mirror when they want to aluminise it was beneath me. They lower the mirror onto this carriage, the carriage moves it away, the crane picks it up and drops it down a hatch into the aluminising tank on the floor below. This thing has big bolts on it, two feet high, one at each corner, and I only just missed one of them. If I'd landed on that, it would have been curtains. I felt I had used up a seven years supply of good luck all in one go.

This may seem a slightly cruel comment, but it's a wonder that dropping so far didn't cure your stammer! In later years you did manage to control it remarkably well. How did you do that?

I found myself at dinner one night sitting next to Mrs Cherry, wife of Professor Tom Cherry who became President of the Academy. Finding out that she was associated with a group of hospital therapists, I plucked up courage (I was morbidly sensitive about my stammer at that time), and asked if she knew anyone who could help me. She did, a Mrs Roma Bottomley of the Royal Alexandra Hospital. I went up to Sydney to see her, she agreed to take me on, and that was great because I knew she was good straight away. I was with her a couple of years, maybe more, at one visit a fortnight. She must have despaired of me at times, but I never did, I knew I was on the right track, and I was quite determined I wasn't going to give up. I thought the family, especially my wife, had suffered enough from it in the past – as I suppose I had too – and they weren't going to suffer any more. I improved slowly, but it took quite a few years – ten perhaps.

Eventually – and extraordinarily – the first time I really came good was when I was attending the celebrations around the Tercentenary of Greenwich Observatory. The celebrations included a symposium at which, to my surprise, I was asked to speak. My paper was to be followed by one from the great Allan Sandage, who is not only an astronomer of the highest class but a very good speaker. I didn't like this at all. I marched out like a condemned man ascending the gallows – but as soon as I was on the steps up to the stage I felt, 'I'm going to be all right.' And I was. It was wonderful.

I talked and talked. The audience was full of knights of the realm and directors of this and professors of that. I had never had to speak to such a high-class audience, so it was lucky I really had something to talk about. I could see that the end of my allocated time was approaching and my chairman, Sir William McCrea, was looking up in a meaningful way. But I couldn't bear to stop this magic fluency and I wasn't going to give up a minute of it! Eventually old Bill had to stand up and wave his arms for me to stop. But that was a fine experience, a great day in my life. I had been improving, sure, but it's a rather up and down thing. That day, though, really altered things for me and since then it's been very much better.

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Into retirement: hanging up the astronomer's hat

You returned to astronomy at Stromlo for a few years before you retired.

That's right. I could have stayed on with the AAT – the Board had offered me a job in Sydney – but by then I felt I'd seen enough of the telescope and it was time for a change. I wanted to see somebody else have a go, and certainly the people who followed me were much more electronically and computer literate than I was. Also, my wife Rosalie's art depended very much on her living in Canberra and having access to a wide expanse of country. To move to Sydney would have ended her art career. I had hoped to clean up the cluster problem with the big telescope, but I came back here.

Actually I found I had got a bit sick of clusters, but by then I couldn't do anything else. It was too late to start, and also astronomy was changing – in the instrumentation, the new electronic detectors being 20 times as sensitive as the photographic plate, in the methods of reduction, with big computers and multi-object equipment like the 400-object spectrograph they've got up there now. The time was when a working astronomer would feel pretty pleased with himself if by the end of his whole observing life he could have produced 1000 or so spectra. But now you could just about do that in one night. It certainly alters things.

The other way in which it is changing is that stars are getting exhausted as objects for study. People really understand stars now, and all their different varieties and ways of behaviour have been pretty well investigated. The interest was shifting very much to galaxies – the normal galaxies, like our own spiral – and also to radio sources and cosmology. That's where the great majority of papers are coming from now. I could never have worked my way into that. Surprisingly, I had no qualms when it finally came to hanging up my hat.

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Putting on the astronomical historian's cap

Now we come to the two strands of the period after your retirement: your return to your early love of history, and assisting your wife in her work as an artist, particularly by cataloguing her artwork.

Yes. When I at last came to retire, Rosalie said, 'You've had your turn. It's my turn now.' But you are right about the history of astronomy in Australia. I do have a number of publications now in that area.

As part of the celebrations associated with the 200th anniversary of the First Fleet, someone had decided that there should be a book on the history of science in Australia. Rod Home, Professor of the History and Philosophy of Science at Melbourne, was made editor, and prompted, I suspect, by Paul Wild, asked me if I would do a chapter on astronomy in Australia post World War II. 'Yes', I said, rather flattered, and duly produced a chapter which I haven't heard much of since, and don't think much of now. It's a good subject though. After the war, astronomy in Australia rose from the ashes to make us in a surprisingly short time one of the leading astronomical countries around, certainly in radio-astronomy, and it is really interesting trying to work out how this came about. Anyway, it got me in. And I must add, really we have maintained our leading position pretty well.

Then I became interested in the old Melbourne 48-inch telescope, which became the 50-inch at Mount Stromlo, and with which I had a lot to do. Why was it such a flop? And how did Melbourne get it in the first place? It seemed incredible that in the 1860s the local government of such a town as Melbourne then was – 10,000 miles from 'civilisation' and all – should approve a proposal for the biggest telescope in the world. These questions fascinated me, and I began burrowing around, sometimes in quite unexpected places, and gradually worked out how it must have happened.

First, how did Melbourne get it? It's a long story, in which personalities abound, as they always seem to with big telescopes. The first director of the Melbourne Observatory was Robert Ellery, a major figure in his day. Previously he had been in charge of the much smaller observatory at Williamstown, where one of his (unpaid) assistants, a certain George Verdon (later Sir George), became very interested in astronomy. Also in politics, before long he was elected to the newly formed State parliament, and within about a year had become State Treasurer, as well as a member of the new Observatory Council. So when Ellery came up with a proposition for however much was needed to buy this 48-inch telescope, which was to be the biggest in the world, no less, he could count on support in the right places. There is more to it than this, much more, but not now.

Why was it a flop? Because it was designed for one purpose only – making hand-and-eye pencil drawings of galaxies. This is a hopeless technique because galaxies are so faint, especially their faint outer extensions, which is where most of the interest lies. They can be seen only with a thoroughly dark-adapted eye, but then you have to light up the paper so that you can see what you are drawing, and you end up drawing not what you can see, but what you think you just saw. David Malin has said that the hand can draw only what the eye can remember, and the eye can remember only what the memory has stored. That's two steps, and you lose a lot at each step. Actually the observers were surprisingly good, and produced some very pretty, delicate drawings – as good as were made anywhere – but drawings of this sort had little impact on the subject, and within fifteen years it had become clear that the way to go was by photography. The Melbourne telescope could not be adapted for photography, or for anything else for that matter, and gradually fell into disuse. It did make a few photographs of the moon, quite famous in their day as the best taken up to that time, but the moon was a special case because it was so bright, and exposures could be kept down to a couple of seconds. Longer exposures were precluded by mechanical considerations – irregularities in the drive and bearing, inadequacies of the control system.

After World War II the telescope came to Mount Stromlo where, thoroughly overhauled mechanically and equipped with new mirrors and a new drive and controls, it came into regular, serious use at last – ninety years after its first installation. It has had a couple more re-buildings since, and is now going better than ever – making a major contribution to a really critical, front-line problem.

I was pleased with this last publication. It was a lot of work, but I think I got it right where many previous people had got it wrong.

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The inspired art of an enduring partnership

Considering Rosalie's enormous reputation in the art world by the time she died, she had entered the field very late in life, hadn't she?

Yes indeed. Her first truly commercial show – her entry into the art world – was held in Sydney in 1976, when she was 59 and had already been in Australia 33 years. It was an immediate success – works being acquired by five public galleries, no less. From then on her progress was meteoric, and she rose to heights she could never have imagined. By the time she died, in 1999, she was being hailed as one of the great Australian landscape artists of the twentieth century – someone who had altered the way Australians see their country, like Fred Williams. A great deal has, of course, been written about her and I don't want to add to it unnecessarily, but my life became so intertwined with hers that I feel I should say something.

First then, she wasn't a painter, and her methods were quite foreign to painting. What she did was to construct assemblages from objects which had been shaped by natural processes like bleaching, ageing, weathering, and decay. Her materials were strictly regional – very much of the Monaro. She found them in Monaro paddocks and rubbish dumps, old cottages, abandoned mines and river banks. Her inspiration came from the Monaro too, but what she tried to convey was not so much the  appearance of our local countryside, rather its  feeling  – the response it aroused in the viewer. She was self-taught, a true original, and she wasn't a traditionalist, nor of the avant-garde, though her art was very much an art of the present. She has described it as 'allusive and elusive': in many ways it was an art-form she created herself. And however high-flown some of this may sound, in practice her work had a transparency, a simplicity, and an intensity which attracted quite a remarkable response from the public – sometimes from most unexpected quarters.

What part did I have in this? On the creative, imaginative side – none. Once she had put her assemblages together, my job was to fix them so that they stayed put. This involved a unique kind of joinery where nothing was straight, or flat, or square, sometimes warped and sometimes not all that sound, and where I had to glue, screw, nail, dowel, or just tie up with wire, whatever the situation demanded. I also introduced her to machine hand-tools, for which she didn't have much aptitude, but she soon picked up what she needed. My great success was a commercial-grade bandsaw I found in Fyshwick. Safe, quiet and quick, she got clever with it, and was soon using it to saw away at her multitudinous soft-drink crates to her heart's content (and to considerable effect). My other contribution was to realise early on that we should photograph everything that left the house. Those albums have turned out to be unexpectedly useful, not to say valuable.

So, the latter part of my life took a totally unexpected turn. Never, ever, had I seen myself ending up as a combination of artist's handyman, cook, and archivist. And never, ever, did I think that I would some day say to myself, as I did when squaring up the panels of one of her best-known works,  Monaro, 'who else in Australia would be entrusted to attack a wonderful work like this with a six-inch circular saw?'. Working with Rosalie could be profoundly satisfying, and I can only say fortunate the man who can claim a place not only in the vital and exciting world of the astronomers, but equally in the vital and exciting world of art.

Ben, I would like to read two marvellous sections from a paper called 'The Artist in Residence', which you wrote in March this year – a delightful piece of whimsical writing, with a lot of interest to it:

'Monaro' is another case in point. It is made of the slats from 40 or 50 Schweppes crates, all of which had to be cleaned and dismantled and the broken or useless pieces rejected. The remainder had to be sawn with the bandsaw into those narrow strips. The bandsaw turned out to have one supreme unexpected virtue: it couldn't cut straight lines – not properly straight. It had a marked tendency to follow the grain in grainy wood. I don't think Rosalie ever consciously worked out what was happening, just took advantage of it, but it certainly made 'Monaro' possible, and the rather similar 'Great Long Paddock'.

I began this article with one quotation. I will end with another. Rosalie was giving a talk to students at the Canberra Art School. The lady who told me this was present. At the end, a student asked, 'What is the most important thing you need if you are setting out to be an artist?' Rosalie replied, 'A partner with enough money to keep you for the rest of your life.' At least I satisfied that criterion.

With that, Ben, we can see you made an enormous contribution to Rosalie as well as to astronomy. Thank you very much for a fascinating interview.

Thank you, Bob, and thank you for being so patient.

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