Zooniverse at Mauna Kea, Day 4: Stand Back!
Tonight we took a brief break from observing galaxies to train the Caltech Submillimeter Observatory on comet Lovejoy. I was able to help out with the observation in a real life version of:
(turns out they have swinging ropes in the control room, who knew?). Sandor and Becky did the actual observing work. Sandor running the telescope, and Becky doing the data reduction to produce a nice graph Chris tweeted:
In the last post, I talked about how the telescope deals with the background noise from the Earth’s atmosphere by ‘chopping’ or alternating reading from its target and a point slightly off the target, then combining the readings to produce a measurement of the target with atmospheric interference removed. This works well for the distant galaxies we are observing, but not with the comet. Chris realized that the comet was too close and large (in a relative sense) for chopping to work. The telescope would take its noise reading while still pointing at the comet.
Instead, we used another, albeit less effective, technique for handling noise. We tuned the telescope to the frequency we were looking for (Carbon Monoxide) took a measurement, and then tuned it to another frequency to measure the background noise. Subtracting the noise measurement from the measurement of our target frequency gives us a clean(-ish) signal.
After that the really exciting bit happened. I got to operate the telescope as we recalibrated it and got ready to point it at our first galaxy of the night. It was pretty easy, telescope operating. Even someone with a BS in Film, like me, can do it. The procedure for moving on our first source was to first pick a bright known object, aim the telescope at it, and have the telescope calibrate its positioning by taking five measurements around the source to figure out the source’s true location.
Once the positioning was calibrated, I ordered the telescope to ‘slew’ (using that new vocabulary) to the galaxy we’re observing, set the exposure time, and then had it ‘chop’. And then ‘chop’ again. And then ‘chop’ again. And again. And you get the idea. I’ve gotten to use a bunch of different cameras, but this was by far the coolest one I’ve operated.
A Few Notes:
- We ran into to computer glitch around 5 in the morning yesterday. Simon, the telescope manager, kindly helped us fix it.
- “Watts/Hertz or Watts*m^2/Hertz” I overheard Becky saying, triggering deeply repressed memories of doing unit conversion in High School chemistry.
- Sorry there haven’t been as many pictures recently. Stuff inside the control room doesn’t really seem to change that much from night to night.
- There was concern about our comet observation from a collaborator. It turns out the telescope was trying to compensate for the comet’s motion as though it were a distant galaxy, so the above graph still needs a few adjustments applied to it.
- We had some Comet Lovejoy themed music tonight . We didn’t even look at M83.
Trackbacks / Pingbacks