A day (and night) in the life of an observational astronomer

Despite what you may think, the day to day life of an astronomer probably isn’t much different to anyone else’s. Most of us spend the majority of the day in our offices, tapping away at a computer, with the occasional meeting and a couple of tea breaks. Sure, we work on some pretty crazy stuff- like black holes and exploding stars and the distant but inevitable demise of the universe– but our daily routine is pretty much your average 9 to 5. That is, until we get to go to a telescope.

It’s important to note that not all astronomers get the opportunity to, or want to, go observing. Some are more interested in taking a theoretical approach, focussing on creating simulations and models to make sense of what we see. They use computers to work out what happens when entire galaxies collide, discover how stars are born, and even create maps of the entire universe. This work is informed by the data collected by telescopes, and in turn, our observations are often guided by the theory. The two go hand in hand, and a lot of astronomers dabble in both.

As for me, I’m more on the observational side of things. My research involves looking for new planets in our galaxy with a telescope called the Next Generation Transit Survey, or NGTS. NGTS detects planets by monitoring the light of thousands of stars and measuring tiny periodic changes in their brightness. If these changes are of the right size, shape, and duration, we can infer that a planet has transited and is blocking some of the star’s light. However, it is possible that something else may be mimicking the characteristic signatures of a planet detection, so we need to take follow-up data with other telescopes to confirm our discovery. This is where I come in.

How we detect exoplanets with NGTS. This is called the ‘transit method’ and involves searching for tiny, periodic changes in a star’s brightness which suggest something small and dark- hopefully a planet- has passed in front of it. Image credit: NASA

Hi-ho, hi-ho, it’s off to a remote desert plateau we go…

NGTS is located in Chile- specifically in the Atacama Desert- which is renowned for being one of the best observing sites in the world. It’s also in the back end of nowhere. This is typical for observatories, which are normally built in very remote places to avoid light and air pollution from towns and cities that contaminates the data. Even with crystal clear air, turbulence in the atmosphere still causes problems, making stars appear to wiggle about slightly, or ‘twinkle’. Whilst this can be pretty when you’re stargazing with your friends on a summer night, unfortunately for us astronomers it means a blurry blob on our images! To minimise the amount of turbulent air above us, we have to get high up- which means the ideal location for our observatories is a mountain or plateau.

The Next Generation Transit Survey at the European Southern Observatory’s Paranal site in the Atacama Desert, Chile. Image credit: G. Lambert

As a result of these requirements, my follow-up observations take me on an 18-hour journey (minimum!) from my home in the drizzly UK to the South African Astronomical Observatory, or SAAO, to use the 1.0 metre Elizabeth telescope. SAAO is a four or five hour drive out of Cape Town, about fifteen minutes from a small town on the South African karoo called Sutherland. The remoteness of this facility, like many others, means there’s no chance of finding a local hotel or AirBnB to stay in, so the observatory has its own specially built accommodation a short drive downhill from the telescopes. This is my home for a week or two while I collect my data.

So what’s it actually like using a big telescope half-way across the world?

The night-to-night life of an astronomer

The biggest adjustment to life at an observatory is being semi-nocturnal. My day starts around 1pm, when a hot breakfast is served, but cereal is on-hand 24/7 if I sleep in later. It can be hard to stay focussed during a long night at the telescope, so the afternoon is a good time to get on with some work. Sometimes I’ll go for a walk and catch some sun; you don’t get to see much of it when you’re observing! Lunch is a hot meal at about 6pm, when all the astronomers eat together- people come from all over the world to use the telescopes, so you get the opportunity to meet lots of interesting people working on all kinds of cool astronomy.

The South African karoo surrounding the observatory.

After lunch, it’s time to get ready to go to the telescope! SAAO has a handy website containing precise up-to-date weather information for the observatory, so I’ll check that to see if the conditions are clear enough to observe (I can also poke my head out of the window to see if it’s cloudy, but unfortunately I’m not fitted with humidity meters and anemometers). If it looks like it’s going to be a clear night, I’ll pack my backpack with my laptop, notebooks, a spare sweater, a few extra snacks (okay okay, the bag is 90% snacks) and my all-important night lunch. This is a little care package of sandwiches, drinks, and nibbles which is prepared every evening for each astronomer, and serves as your dinner. Trust me, there is nothing better when you’re observing than a 3am cheese toastie and a hot chocolate!

The drive up the mountain is short but beautiful as the sun sets over the South African karoo. Occasionally I’ll see springbok or dassies on the way up- one time, there was even a lion on the loose by the observatory (but that’s another story).

Once I get to the telescope I’ll head to my office for the night, which is a small room to the side of the main part of the dome. Although it may sound romantic, using a telescope doesn’t involve me sitting at one end and peering through an eyepiece all night taking notes! Nowadays, the light is collected by a camera, and astronomers sit in a control room with computers and buttons to control the telescope. This ‘warm room’ is usually located a bit away from where the actual instrumentation is housed, so that every time you open the door light doesn’t shine into the telescope and contaminate your data.

The warm room in the 1.0m telescope at SAAO- my office when I’m observing!

At the start of the evening I switch the camera on. Even though I won’t be taking data for a while yet, the detector needs time to cool down to a chilly -50 degrees Celcius, which keeps instrument noise to a minimum. While I wait, I have a few minutes to stand outside and watch the glorious African sunset.

Sunset at SAAO. The 1.0m telescope is at the forefront of the image.
Here I am at sunset, just outside of my telescope dome! Behind me is Lesedi, another 1.0m telescope. Earth’s shadow, the dark band below the orange and pink of the sunset, is visible above the horizon.

Then, it’s time to get to work.

The first thing I do when I start my night of observing is take a few images with the telescope shutter closed, as well as some of the blank sky (before the stars appear). It sounds weird, but these ‘bias’ and ‘flat’ frames are really important for calibrating the science images I’m going to take later, as they account for tiny fluctuations in each pixel of the camera. Ignoring these could ruin the precise measurements I need to make.

Once it’s dark enough, it’s time to take a look at my targets. I’ll move the telescope to point at the right part of the sky and find my star using a finding chart. I also need to find a nearby bright star to use as a ‘guide’, which the telescope uses as a reference to help it to stay pointed at the same place in the sky as the Earth rotates. The guide star is also a useful tool with which to check the atmospheric conditions, like how “twinkly” the stars are, which has an effect on the quality of our data.

After I’ve found my target and guide star, it’s pretty much a case of setting the exposure time and number of exposures and hitting go! Planet transits usually take a few hours, so I’m able to basically let the telescope do its thing whilst I get on with some work, or, later in the night, watch some TV or a movie (and eat all those snacks). I’ll keep an eye on the weather and guiding to make sure the data is okay; occasionally when the conditions get really awful, I’ll have to guide by hand, which means moving the telescope by tiny increments every few seconds. It’s not the best way of stabilising the telescope and if the weather doesn’t improve it typically means it’s time to call it a night.

Sometimes, if I’m feeling brave, I’ll step out of the comfort of the telescope dome and into the inky outside world to look at the stars myself. A clear night sky, viewed with your own eyes, is completely breathtaking, and I implore everyone to try stargazing (properly, away from a city or town) at least once. Due to the lack of extra light around you, the Milky Way becomes immediately visible as a river of stars and dust overhead, and as your eyes adjust to the low light the picture only gets more beautiful as more stars become visible. Being in the southern hemisphere, you’ll also notice two fuzzy blobs– they look like clouds- to the side of the Milky Way, which are in fact dwarf galaxies. Each blob contains billions of stars and are hundreds of thousands of light years away, and yet it feels like you could reach out and touch them. I feel extremely fortunate to be able to visit parts of the world where the night sky is so magnificently clear, and yet, I also find leaving the dome and stepping into the silent, pitch black all alone slightly terrifying, so I don’t go stargazing when I’m observing as often as I should.

The night sky over SAAO. The telescope silhouetted in the image is SALT, or the South African Large Telescope- so called because its primary mirror is 10 metres in diameter! The Magellanic clouds are visible just below the Milky Way towards the centre of the image.
Image credit: Chantal Fourie

Back in the dome, and back to work. If the night goes smoothly, I’ll be taking data until just before sunrise. As the sky gets lighter, the data quality decreases as the stars start to fade away into the background of the morning sky. I make sure to shut everything down, including closing the shutter and the telescope dome, before packing up and heading out. The drive back down the mountain is a slow one as I’m not allowed to put my headlights on in case other astronomers are still working, so all I can use are my hazard lights until I get closer to the hostel.

When I finally get back to my room, I’m pretty exhausted. If I’ve had to shut down early due to the weather, I’ll need to fight off sleep a little longer and stay up to keep my body clock in line with my new nocturnal lifestyle. Otherwise, if everything’s gone to plan and I’ve managed a full night at the telescope, I can collapse into bed just as the birds are starting their morning chorus. Either way, if I’ve managed to get some data, I’m a happy astronomer! And if I haven’t, there’s always tomorrow night…

A final note: experiences come in all shapes and sizes

Observing can be exhausting, exciting, frustrating, and awe-inspiring all at once. However, not all astronomers will have the same stories and no two observing trips are the same. In this article, I’ve shared my own experiences, but this is one telescope at one observatory looking at one particular thing. There are lots of different types of telescopes and lots of different ways to measure the weird and wonderful things we study in the night sky, so I encourage you to ask other astronomers about their own experiences! Maybe their science has taken them to an observatory in Thailand, or they’ve studied the Universe using invisible light, or had the opportunity to sit at the helm of one of the largest telescopes on Earth. And who knows, maybe one day you’ll get to have an observing experience of your own.

About Rosanna Tilbrook

I'm a second year PhD student at the University of Leicester. My research is centred around the Next Generation Transit Survey, which is a telescope in Chile looking for new planets in our galaxy by measuring minute changes in the brightness of stars. When I'm not doing spacey things, I like to listen to / play music, travel, eat pasta, and squish my cats.

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  1. Thanks for your sharing. Really get me looking forward to my first observation, especially a lone one!

    • Really worth sharing. Encouraging people like me who are planning for astronomy career.

  2. Very interesting Rosanna. Thanks. As you are at Leicester university I am going to post this on the Leicester astronomical society Facebook page. Perhaps you would like to come and talk to us when we resume meetings again at some point in the future please?

    • Hi Ann, that sounds great! Feel free to drop me a line when things are back up and running- you can find me through the University webpages, or on twitter (@planet_rosanna).


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