On Wednesday, while staying at Davis Mountains State Park, we headed further into the mountains for a McDonald Observatory tour. The drive was, as always, spectacular. The McDonald Observatory is on the Fort Davis Chamber of Commerce Scenic Loop. Broad vistas, amazing rock formations, Civilian Conservation Core roadside turnouts and at steep twisty turning mountain road complete with a rusting hulk of an ancient wrecked car wedged into a cliff crevasse.
Amazingly, the sundial on the plaza in front of the visitor center tells time. The day we went, during daylight savings time, the sundial was an hour off. I guess they haven’t made a sundial yet that can deal with daylight savings time.
The last tour of the day started at 2:00 PM and lasted about two and a half hours. We arrived early and watched a 15 minute informational video (revised since the last time were were there).
Just before two, the theatre started to fill up. A lecturer appeared and began a presentation on the sun that included live video from the solar observatory. This was our first time experiencing the solar lecture. She talked about sunspots, solar prominences and solar flares. We got to see live video feeds of our sun. Unfortunately, in the solar cycle, this is a relatively tame year so sun activity was at a minimum.
According to the lecturer, we had a 50% chance of seeing a sunspot. We were lucky. There was one tiny sunspot visible.
The solar prominences were also small.
Since there was only one sunspot and it was a tiny one, there were no solar flares. This is good news bad news. Good news for communications networks and power grids. Bad news for geeks like me who want to see a solar flare live.
Toward the end of the solar lecture, Linda leaned over and let me know this level of science detail was well over her pain threshold. My version of this pain is one of Linda’s budget meetings where I quickly grow bored. I can relate.
At the end of the presentation, the solar lecture only people were dismissed. The full tour people (like us) were asked to stay in the auditorium. The telescope tour guy introduced himself. Next, he covered logistics. We were encouraged to drive our own vehicles up to the telescopes because the group was larger than the van seating capacity. People with mobility disabilities were encouraged to ride the observatory tour bus with him. He went on to say that really anybody could ride the tour bus if they wanted. People who drove their RV to the observatory should also ride the bus.
He was crystal clear that motorhomes, vehicles pulling trailers or other large RVs were not allowed on the roads up to the telescopes. Large vehicles simply can’t park or turn-around in the available space. Additionally, the road is extremely steep (20 plus % grade?) in places adding an additional complication for large vehicles.
These logistics were somewhat different than our tour from 15 years ago. Back then, no private vehicles were allowed anywhere near the telescopes and everyone rode in one of two vans. Personally, I prefer being able to drive my own vehicle so this is a good thing.
Something else our tour guide said that intrigued me. After giving driving directions to reach the first telescope on the tour, he said, “We will meet at spot number 3 on the self-guided tour. Just look for a large number 3.” This is the first time we heard anything about a self-guided tour.
We all lumbered out of the auditorium past the gift shop and through the doors.
Pulling out of the parking lot, we turned left in front of the visitor center. Past the visitor center is spur 78 where we turned right to go up the hill. At some level, the drive up the mountain where the Otto Struve and Harlan J Smith Telescopes are is thrilling. In places, we could hardly see the road ahead as it disappeared under the Jeeps hood. The first telescope, the Otto Struve Telescope, loomed ahead on the mountain top.
The parking lot is slightly downhill from the the first telescope. We parked next to an old (abandoned?) dilapidated 1970’s Chevy pickup. I recognized the pickup from the mountaintop aerial and satellite views from the visitor center videos and presentations. I recalled the presenters purposefully pointing out the pickup but never understood its importance. I still don’t get the joke.
On the way up the hill, past the Otto Struve Telescope, is a sign pointing out that the road we were walking up was the highest elevation state road in Texas.
The two pay telescopes to the right of the sign enable viewing features in the broad valley a few thousand feet below. To the right of the pay telescopes, there is a box with Self-Guided Tour pamphlets available for $1.00 donation.
The tour meet up point was on the backside of the Harlan J Smith Telescope. First we walked uphill past the Otto Struve Telescope.
Past the Struve Telescope the hill sloped down to the Smith Telescope. Before reaching the second telescope, I turned for this view of the Struve.
Continuing down and to the right, the Smith Telescope revealed itself.
Slipping past the right of the telescope was a huge liquid nitrogen tank. We heard later the nitrogen was used to cool critical instruments to keep electrical and optical noise to a minimum.
Past the nitrogen tank was the number 3 sign we were looking for. We beat the tour guide and bus riders to the marshaling point so we had time before the others joined us to look at the view. At this point, Linda pointed out a deer munching grass on the steep slope below us.
After the bus arrived and its passengers arrived, the tour guide began to talk about what we could see from the viewing point and why all that was important.
Tour Guide Shout Out – Our tour guide was awesome, totally into and excited by the whole astronomy thing.
Then we were instructed to enter the telescope building from the back entrance and wait.
Once everyone had gathered, the tour guide talked through each of the informational displays on the walls.
The tour guide told us there were 70 plus stairs to the telescope base. Anyone who wanted to could take the elevators instead. Once upstairs, we were instructed to stay outside the green line. The stairs are somewhat claustrophobic, narrow and steep.
The telescope is the first thing noticed when entering the dome. It dominates the dome. After everyone arrived, we stood around the edge of the dome as the tour guide talked about the telescope’s design and features. He invited audience members (children until he ran out) to push the buttons that manually move the giant telescope into position. In addition to moving the telescope, he also demonstrated (with audience participation), how the dome rotated and how the canvas shades could be moved. He didn’t open the outer doors. The dome’s interior is cooled to the expected nightly outside temperatures to minimize issues with condensation and thermal warping of critical components.
In the above picture, to the left of where the tour guide is standing, is a heavy cardboard tube. This is a model of the telescope. The tour guide took it apart and reassembled it to show us how the telescope works. I thought this was so cool. It was at this point that Linda told me she had had enough of the geek stuff. Fortunately, at this point, we were ready to go on to the next stop in the tour.
We went down the way we came up and out the door we came in. Back at our Jeep, we headed off to the next stop. Downhill to the saddle between mountains and then back up hill to the Hobby-Eberle Telescope.
The parking lot is tiny. The gathering point for the tour was in the lobby.
Inside the lobby are a number of infographics and displays related to astronomy and the telescope. There was also seating. Linda sat down and said, “Take all the pictures you want.” So I did.
While the tour guide spoke, I snuck off to the back wall. A large set of windows separate the lobby from the dome. From the windows, I could easily see that this wasn’t an ordinary telescope. That was what the tour guide was saying. What is similar to many other large telescopes is that it has mirrors that reflect and focus light from the heavens to a detector. The mirrors are on the bottom and the detector is above.
In the above picture, look for the mirrors. They are hung on top of the blue-green pipes. The prominent white pipes and metal scaffolding surround and support and the blue-green mirror and sensor assemblies. Below, the picture zooms in on a particular area of the mirror assembly. Individual mirrors can be seen. The mirrors are reflecting the white support structure above them. What can’t be seen in the pictures is the sensor array. Sensors are located above the mirrors and are aligned with the mirrors so that light reaching them is in focus.
The following picture shows how individual mirrors are attached to the assembly.
In short, this telescope doesn’t look like or work like a traditional telescope. Apparently, it is the world’s second largest telescope.
After answering questions, the tour guide dismissed us and we were on our way.
Remember how RV’s weren’t allowed on the roads up to the telescopes? Not everyone is a quick learner.
The drive back to Davis Mountains State Park (link) was every bit as spectacular as the drive to the McDonald Observatory.
By the way, the visiting astronomers stay in the building below the telescopes.
While getting our tour tickets, we also signed up for the Friday night star party. More on that later.
Hope to see you on the road ahead!