Astronomy from the inside

About a year and a half ago my husband and I were lucky enough to accompany an astronomer to Palomar Observatory as he set about installing a new instrument on the 200-inch Hale telescope.

The astronomer who invited us, Gregg, is a professor with the energy of three people, and the talking speed to match. Gregg and his colleague, Leon, along with a few other astronomers and engineers were at Palomar to install an instrument designed to search for low mass planetary bodies in the outer solar system.

Although I’ve since been lucky enough to visit Magellan, Gemini, and Cerro Tololo in Chile, and I’m working on the project to build the next great telescope, at the time this was my first visit to a working optical observatory. My husband is a radio astronomer, so he was equally at sea.

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200-inch Hale telescope dome at Palomar Observatory

We arrived from Pasadena late on Friday night, driving up Palomar mountain in complete darkness, and met Gregg outside the dome of the 200-inch. Our eyes had adjusted for only a few seconds when we saw the spectacular sky. Gregg however, was not happy. They had just spent the day installing the instrument, but now they couldn’t start observing because of the humidity.

This was lucky for us however, because we got a quick tour of the inside of the telescope dome – the adaptive optics lab, the control room, and after checking behind approximately ten identical doors, the pool table. Gregg then took us up several flights of stairs, along corridors, past the giant telescope, through a heavy door and outside onto the catwalk. Once we became accustomed to standing on a see-through gantry, we looked at the horizon and saw the marine layer of clouds sitting over San Diego. This is what was causing the humidity problem. But not one to stand still for a second, Gregg got out his camera and tripod and took a bunch of photos of us with the Milky Way in the background.

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The 200-inch up close.

Then, all of a sudden, the catwalk started moving – the dome was rotating! We headed inside to discover that the humidity had dropped below the required amount, and now they were turning the dome to various angles to the wind to dry it off in the gentle breeze.  It would be unfortunate, after all, for a big drip of moisture to land on the 5-meter wide mirror.

An hour later, the telescope operator pronounced the dome to be sufficiently dry and started the procedure to open it. At once the control room was a flurry of activity. Four astronomers huddled around the control system, changing settings, asking the support astronomer to move to different stars as they tried to adjust focus. Once everyone was happy, they asked for the telescope to be moved to M22 – a globular cluster. The stars filled the field and the focus was adjusted some more. The “seeing” was sub-arcsecond, which is remarkable but also not surprising: there is a good reason the Palomar Observatory is located where it is. The image on the screen was very clear but things were not working to the astronomers’ satisfaction.

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Inside the control room

By 3am, with the instrument still not working, my husband and I were finding it hard to stifle yawns. The rest of the team were already tuned into the night cycle, so Gregg took pity on us and drove us down to the Monastery. We stupidly crept about trying not to make any noise before realizing it didn’t matter because everyone was at the telescope. We slept behind blackout curtains in a comfortable bed surrounded outside by a very peaceful forest while the astronomers worked until dawn to debug their problem.

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The Monastery

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Spartan but comfortable

We were up around noon, and after having a very quiet breakfast in the communal dining room we went for a walk on the site. We saw inside the 200-inch dome from the ‘tourist’ side and checked out the small but impressively informative visitor center.

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George Ellery Hale

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Concrete blank of the 5 meter mirror

Later in the afternoon we headed down to the dining room and met up with everyone again for coffee. The discussion was of continued issues with the instrument – they had not been able to solve the problem last night. We were treated to the story of how the original version of the instrument was designed and built in only a few months, and how for some parts it was simpler to use a Canon camera lens and an amateur telescope, and how 24 hours before the instrument was due at Palomar it was sitting in 100 pieces on the floor of the lab in Pasadena.

To pass the time before dinner, Gregg took us up on the catwalk of the 200-inch again to see the view in daylight. Tourists below us asked “how do we get up there?” “Sorry,” we called down smugly, “you can’t”.  Then as dinner time approached Gregg gave us a tour of the other telescopes on site, trying to remember what key opened what telescope dome and giving us a rapid history lesson at each one.

Discussion at dinner was of giant telescopes, and what they would mean for the future of astronomy.

Once it was dark, we all headed back to the 200-inch. I brought my film camera and tripod ready for a night of long exposures and star trails. But, all was not well in the control room. Something still wasn’t working, and as the evening began, the astronomers continued to debug their system – one person on Skype in Pasadena, another at the prime focus right at the top of the telescope, the third in the control room.

At this point Gregg suggested that my husband and I should take this opportunity for a visit to the prime focus. For an astronomer geek this is just about as exciting as it gets.

We went up from the internal catwalk in the world’s slowest “elevator” until we were 17 meters above the priceless mirror (luckily with its cover on). Leon and his colleague switched out cameras and used an alarming number of cable ties to secure everything into position. Aluminum foil – light-tight and excellent for keeping things dark – was used in abundance.

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Working on the instrument at the prime focus

Back down in the control room, we sat around for a while, then decided to make the most of the ‘free’ time while debugging continued to go outside take some star-trail photos. We set up and were out for what seemed like an age (probably a couple of hours), looking at the stars, and spotting the occasional meteor or fireball.

Cold and with sore necks from looking up, we headed back into the telescope, having luckily remembered where the door was, which while it never moves, is also is never in the same place relative to the opening of the dome. The mood in the control room was jubilant – the problem had been fixed and they were taking real data. Soon, the music was cranked up, and celebratory refreshments were passed around.

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That evening I reflected how lucky we were to have such an opportunity to visit what was once the world’s largest telescope, to have an instrument builder take his time to show us everything and involve us in his work. As is required now and again, when the day to day of work seems so far removed from what we are ultimately trying to achieve, this visit rekindled my passion for astronomy and reminded me why we strive to build giant telescopes: to enable astronomers to do their magic and push the frontiers of human knowledge.


Thank you Gregg for an amazing weekend!

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