A short history of Scotland’s largest telescope

‘University Observatory’ and ‘James Gregory Telescope’ says a blue sign on the outskirts of St Andrews, one mile away from the historic cathedral. If you drive slowly along Buchanan Gardens, you will see a collection of dome-shaped buildings, hidden by belts of trees and surrounded by university playing fields. Inside the biggest of these weathered domes is the James Gregory Telescope. To this day, it remains the largest telescope ever built in Scotland and one of the largest operational telescopes in the United Kingdom. It is also a living anachronism — an active research telescope located right next to a university, under mostly cloudy skies, not in a remote place at the other end of the planet, like most other big research telescopes today.

As I am writing this, members of the University and College Union, including myself, are on strike. We are protesting the slashing of pensions for lecturers, by a lot. The stakes are high. It is about pensions, yes, but it is also about so much else. For this sector and this country, the strike is unprecedented in scale, in energy, and in sacrifice. As of right now, I am the only university employee who can fully operate the telescope, and therefore, while we are striking, the telescope stands still. The new camera will not be installed. Students will not be trained. Tours will not be given. Stars will go unobserved.

The history of a telescope can be presented in a variety of ways. When viewed from inside the organisation, we tend to describe the present as the outcome of a logical sequence of achievements, one building on top of the other. In this process of white-washing, we leave out the struggle, the flaws, the workarounds, the conflicts, the interesting bits. When I am talking about the JGT in public as part of my job, I am creating a telescope that is just a little too perfect, that bears only superficial resemblance to the thing in front of me. But I am on strike now. I am not writing in my function as Director of the Observatory. This is an inofficial narrative of Scotland’s largest telescope.

The domes of the observatory, made transparent by Joe Llama. The JGT is on the left.

The James Gregory Telescope is a unique machine with a unique history, the largest telescope ever built with the Schmidt-Cassegrain optical design, a creative combination of two spherical mirrors and a thin aspherical lens. In the ideal case, this design allows for a very flexible telescope configuration, combined with an undistorted field of view of about sixty times the size of the full moon, or sixteen square degrees. That’s a lot, even when compared with wide-field telescopes constructed today. The Schmidt-Cassegrain is the perfect design to monitor large numbers of stars, to search for faint objects, to scan an extensive area of the night sky.

Stigler’s law of eponymity states that no scientific discovery is named after the discoverer. In the 17th century, James Gregory invented a telescope, but not ours. In the early 1940s, Baker and Linfoot invented the design named after Schmidt and Cassegrain. In both cases, the telescope started on paper, as a series of sketches and equations. The “SC” is not the easiest telescope to build. Not that telescopes of that size are ever easy to build. For the staff at the just founded observatory in St Andrews it was a daunting, but welcome challenge. Erwin Finlay-Freundlich, the director of the observatory, worked most of his career as a solar astronomer and had never built a night-sky telescope. Robert Waland, the lead technician, was a self-taught telescope builder from Dumfries who had never worked at a university before.

They figured it out, although it took about twenty years from the initial idea to the inauguration. These twenty years include the construction of a half-sized pilot version, a little brother to our big optics. Waland’s hand-drawn sketches show thousands of parts, all unique, all made just for this telescope. In black-and-white footage, Finlay-Freundlich and Waland are seen standing next to their half-finished mirrors, making serious faces. The James Gregory Telescope is a true home-grown telescope. Converted to today’s money, the whole thing had cost the university and various funding bodies around one million pounds.

Considering how much work and money was invested in the big telescope, it is surprising how unproductive it was over most of its existence. During the three decades starting from “first light” in 1962, the photographs from the telescope were only used in a handful of peer-reviewed publications. It’s not that the telescope wasn’t used — it was observing more or less continuously, making use of a good fraction of the clear nights in St Andrews. PhD students did research. Undergraduates learned how to observe. But there was no coordinated long-term plan for systematically exploiting the telescope. In university footage from 1971, the James Gregory Telescope features prominently as a major piece of equipment, but no word about its scientific achievements. It appears that the telescope was, at first, an object of prestige for the university, and an object of pride for the astronomers, but not so much a scientific instrument.

One of the early shots from the telescope. The Leo triplet, a small group of galaxies, observed by Chris Fraser.

From the beginning, the telescope was flawed. Not doomed, but flawed. For a Schmidt-Cassegrain to give clean images, the lens has to be shaped in a very precise manner. And it’s not a simple shape. One of the surfaces is flat, like a window plate. The other has a peak in the center, surrounded by a circular trough, about a quarter of a millimeter deep, before becoming thicker again towards the edges. It is remarkable that Waland was able to manufacture a lens like this, with a size that remains one of the biggest of its kind in the world. To this day, we cannot quite figure out how he did it. And he made a slight mistake. The plate is “too strong”, in the sense that the trough near the edges is 1/50th of a millimeter too deep. Nineteen micrometers, to be precise. The bottomline: The stars appear blurry.

The mistake was corrected in the late 1960s by moving the main mirror two inches further away from the lens, a dirty workaround, a temporary solution, which stays with us until today. Because of that, the focal plane of the telescope, the place where you need to put the camera, is now in the hole in the center of the primary mirror, in a very limited space. The field of view of the telescope, its main feature, was reduced to about five square degrees. This is still huge, but what a disappointment compared with the original size. The only way to make the telescope fully functional would be to dismantle it entirely and repair the lens. Or to buy a new one.

The James Gregory Telescope today, at work during a clear night. (Photograph: Jan Bölsche)

It appears that over the course of the years, maybe starting with the inauguration, the university lost interest in its big telescope. Never was there any provision made for hiring dedicated observers, people who are paid to stay up at night to exploit every clear hour. Lecturers and students tried to combine observing at night with all the other work during the day, often ruining their sleep pattern. The observatory workshop was moved off site in the early 1990s. People with crucial expertise left or retired without being replaced. Routine maintenance jobs, like the resurfacing of the mirror, were not done anymore.

Around the same time, the university invested heavily in a new astronomy group in the new School of Physics & Astronomy about a mile away from the observatory. The group would grow over the next two decades and do fantastic research, either in theoretical astrophysics or with telescopes in places with much better weather. Or in space. The old telescope on our own campus was left with a shoestring budget, inadequate for a machine of this size. A funding application from the mid 1990s, describing the observatory, speaks of an “ambience of decay”.

If you walk to the observatory on a winter evening, you would not think that this is a place to watch the stars. Until ten o’clock, the adjacent football pitch is illuminated by super-bright floodlights. Our domes are right next to them. It is an incongruent picture, the big telescope and the beam of light, so weird that it takes a moment to realise the conflict. Here, the university is following one of the key laws from the field of Systemantics: Systems tend to oppose their own proper function. The lights are baffled and directed to the ground, but still, the stars don’t stand a chance against them. The flood lighting started encroaching on the observatory in the mid 1990s. It effectively ruins observations by eye, astrophotography of faint targets, and teaching in the early evening hours. It seriously impacts the choice of research programs at the James Gregory Telescope. Obviously, around here sports is more important than access to a dark night sky.

Floodlights next to the observatory. (Photograph: Jan Bölsche)

Paradoxically, the telescope became much more effective in its old age, despite the lack of support and despite the floodlights. It is almost as if the telescope had to be forgotten to take on a new life, as if it had to find its niche outside the constraints of the university life around it. Another key insight from Systemantics: Choose your systems with care. In the 1990s, our telescope started to produce a couple of papers every year, thanks to tailored research programs led by astronomers Ron Hilditch and Andrew Cameron, and thanks to collaborations with astronomers world-wide. Over the last decade, the James Gregory Telescope contributed to the discovery of exoplanets, by observing the dip in the brightness of stars when the planet eclipses them. It observed minor planets, young stars, active stars, space debris.

Over the same timespan, the technology and the infrastructure was modernised and upgraded, primarily due to the voluntary work of Roger Stapleton, a retired astronomy graduate and IT expert, and supported by a couple of generous donations. The observatory became more accessible and more comfortable, with Wifi, proper heating, new furniture, refurbished rooms, new paths. Some keen students discovered that it was a place to hang out, to explore the nightsky in their own time, outside the constraints of the curriculum. Every year, up to a thousand people visit the observatory and see the James Gregory Telescope in action. Today the telescope is still working with its old core, but it is operating like a 21st century telescope. Almost. Out of the ambience of decay grew something new.

One of the best images from our archive: Nebula and bright stars in the belt of Orion. (JGT plate, 1984)

But this won’t last forever. Telescopes as big and complex as the JGT, like all large technological facilities, need staff for maintenance, management, and operations, plus a substantial budget to cover costs for new parts and contractors. They need to be continuously supervised, developed, documented. They need a plan and a vision and a flexible support structure. At the minimum, it needs to be recognised that telescopes are a long-term investment, and not a one-off experiment. A functioning telescope, properly maintained, is always useful, even when based in a location with many cloudy nights. Telescopes like ours do not die because of technical failures or bad weather, they die when nobody cares for them. Exactly that happened to the other large telescopes in St Andrews, and the same thing will happen to the JGT, eventually.

The double aperture 40-cm Twin telescope was dismantled in the late 1990s after a good decade of operations and after an upgrade to the control system remained unfinished due to lack of funding and manpower. The 50-cm Leslie Rose Telescope reflector is still in place in a small building on top of the old observatory building. It is lacking a camera and has not been used for most of the last decade. The half-scale pilot model, the progenitor of the James Gregory Telescope, was scrapped in the 1990s because there was no space to store it. Its mirror remains as a museums piece. All three telescopes gradually disappeared from our collective memories. Their stories will need to be written another time.

For a much more detailed account of the observatory’s history, see Ron Hilditch’s book “Stars over St Andrews”, available through the university library. For information on open nights and tours, please visit the observatory website.