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Ay/Ge 107 Palomar Trip

Last weekend, I had the opportunity to stay two nights at Palomar Observatory with my Intro to Astronomical Observation (Ay/Ge 107) class. Palomar Observatory is an observatory owned and operated by Caltech and located in the Palomar mountains in San Diego. This is the second year Ay/Ge 107 was offered, and I had heard good things about it from the previous year’s students, with this mandatory trip being the highlight. 

Ay/Ge 107 teaches introductory techniques for using telescopes to observe celestial bodies and analyzing data collected from telescopes. Throughout the term, we have weekly lectures and several nighttime observing sessions on the roof of Cahill, Caltech’s astronomy building, where we gain experience using portable Alt-az and Equatorial telescopes. Outside of this structure, the class centers around designing and completing one scientific project using data collected from our weekend stay at Palomar. While relatively fast-paced, I felt that the work we put in during the first few weeks led to a rewarding and well-planned observing session at Palomar. It was the perfect weekend getaway, balancing science and mountain retreat.

Day 1

Palomar mountain was a bumpy 2.5 hour van ride away. On the winding road up the mountain, it was so foggy we could scarcely see 5 feet in any direction. We arrived in the afternoon at cozy accommodations. The place we stayed at was called The Monastery, a spacious 12-room lodge with dining and lounge spaces about a half mile walk from the 200-inch telescope where we would be observing. It was a dormitory meant for hosting visiting astronomers. Each room was outfitted with blackout curtains to enable  guests to sleep during the day and stay up at night observing; such is the life of an astronomer.

We were greeted by two staff, Alex and Brian, who helped us get settled and promised a good dinner surprise. According to our professors, Palomar has famously good food. Dinners are cooked in-house by kitchen staff, and they had us send in our dietary restrictions a week in advance in order to purchase and prepare ingredients. In addition, the kitchen is stocked with microwave meals, breakfast foods, and snacks.

Since the afternoon was relatively free, we walked to the dome to take a tour of the telescope and get a headstart on our calibrations, as  these could be taken before it was dark out. 

Later, we headed back to the monastery for dinner before finishing the rest of our calibrations. Unfortunately, it was too cloudy that night to see anything in the sky – we were at the whims of the weather. Again, I learned that such is the life of an astronomer. At least we were able to sleep at a normal time.

The outside of the dome. The dome roof has a slit which opens up to allow the telescope to see the sky at night
Inside the 200-inch telescope. The large bar in the front helps rotate the telescope on one of its axes. The 200-inch measurement refers to the diameter of the mirror used to college and focus light towards the eyepiece.

Day 2

Because all of our observations occur at night, the day was pretty much free to us. Palomar observatory has three active research telescopes on the mountain, connected by convenient paved paths. My group mates and I decided to enjoy the fresh air and walked to each one – there were the 18 inch, 60 inch, and 200 inch telescopes. The location of the 60-inch telescope had the best view of the mountains and the valley below.

After dinner was when the real work began. 

In the previous few weeks, we had researched targets, gathered coordinates, calculated brightness and exposure times, and learned how to process image and spectroscopy data in preparation for our session at Palomar. We were given a lot of freedom to work in small groups and choose our targets and scientific questions. My classmates chose a variety of cool projects, including recording the spectra of eclipsing stars and observing interacting galaxies. My group chose the galaxy M101, aka the Pinwheel Galaxy, as our target for observation. We decided to image the galaxy under four different filters in order to analyze the emissions in different regions of the galaxy. These could give us information about the temperatures and age of stars in different regions of the galaxy, as well as allow us to see the location of star-forming regions in the galaxy arms. Furthermore, we expected to be able to assemble our filtered images to produce an impressive false-color image.

Now at Palomar, the weather was still looking iffy, but it was about 30% better than the night before, which was luckily just enough so that we could open the telescope dome and observe. The telescope operators gave us a demo on how to use the WaSP imaging instrument and input our coordinates, exposure times, and set filters, and assisted us with any questions we had about using the telescope. 

(Left) NASA image of M101. (Right) Raw image we took of M101 under the H-alpha filter at Palomar. H-alpha is a narrow-band filter (it only detects a small range of wavelengths) and shows the galaxy’s star-forming regions.

Luckily, the weather continued to stay decent throughout the night. While the dome had to be closed a few times due to high moisture content, every group in our class was able to get some data for their projects. 

The big dipper. Our galaxy, M101, although not visible with the naked eye (or with the iPhone camera), is located slightly above the big dipper’s arm.

Day 3

Just packing up and leaving. The Monastery guest book was filled with a host of other Caltech-affiliated visitors, to which we added our names. We took a bit of extra time in the morning to walk back to the telescope and check out the view from the catwalk, which snakes around the perimeter of the dome.

The remainder of the class will be about analyzing scientific data, including quantifying uncertainties and working with astronomical survey data from publicly available sources. We will have to process and analyze the data we collected ourselves to answer the scientific questions we designed, which will be pretty exciting. Maybe I’ll report back when I have colorized our images :).

Thanks to the Palomar staff and our profs for making it an amazing trip.

Vivian Zhang '24
Vivian Zhang

Hi! I’m Vivian, a senior from New Jersey majoring in Computer Science. I’m a member of Lloyd house and Pipettes, one of Caltech’s a cappella groups. In my free time, I love swimming, drawing, and going for long walks.

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