Wednesday, July 3, 2013

Astronomy: Las Campanas, Round Two

Las Campanas Observatory

This past weekend, I took another short trip to Las Campanas Observatory for a brief observing run. Given that my experience this time was different, and that perhaps some readers may want to learn more about the life of an astronomer, I've written this short post on my recent time there.
At least one paragraph is very science-y, so feel free to skip that one if you're not an astronomer ;)

More after the jump.

The first notable difference from last time (see here) was the lack of people. Previously I had arrived just in time for a bunch of VIP visiting the observatory, plus a large group of engineers was hard at work with MagAO, the new adaptive optics system at Magellan. This time was far quieter with only the basic support staff and observers present.

An HDR-like picture of some of the plants near the dorms and dining hall

For this run I only had a single night on the 2.5 meter du Pont telescope. I had used the instrument before (B&C spectrograph) and, curiously enough, a friend of mine from Santiago was going up to use it for the first time the next night. He and his student showed up to look over my shoulder and learn the ropes. It was a win-win situation since I had some extra company and they got a chance to see the instrument in action before their run.

The run itself went great. Clear skies, good seeing, and no telescope or instrument failures. I had overestimated my exposure times (my setup was different from last time), so I changed this on the fly and was able to observe more targets than I had anticipated. Check out below to see how some of the extracted spectra look like. I'm excited to start analyzing these data!

Sample B&C spectra taken at the du Pont telescope; normalized at 6300 angstroms. The spike at 6563 corresponds to Hydrogen emission. Different spectral types (ie, temperatures) are responsible for the overall shape to the spectrum.

These targets were mostly M-stars, as expected based on my selection criteria. For the astronomers out there, these spectra were taken with the 832 line/mm grating at an angle of 21 degrees. I note that the javascript calculator online was not returning the right angle to get the coverage I wanted. The slit size was 100 microns (~1") and the seeing was very good. I wish I had more time with this instrument!
A minor setback, however, is that the spectrum cannot be perfectly focused across all wavelengths. I had completely forgotten about this and the operator went ahead and focused where the arc lines were brightest: in the red around 8200 angstroms. The full-width at half maximum (FWHM) for the arc lines in that area is about 2.2 angstroms, but in the bluer part of the spectrum the FWHM reaches 4 angstroms. Alas, I wanted a resolution of about 3000 or more around 6500 angstroms and yet got a lower value there. Not a show-stopper, but it means faint features in that area of the spectrum will be hard/impossible to spot and will limit how much I can do.
In the future, I may have to sacrifice spectral coverage so I can get the resolution I need, or consider using another instrument. Interestingly, there aren't that many medium-resolution optical spectrographs available in Chile on small/medium telescopes...

An old photographic plate at the du Pont from back before CCDs were invented. You can see stars and nebulosities!

The night was long since it's winter here in Chile. This is of course good for science (lots of targets!), but it leaves you exhausted. A small price to pay for science, though.
Unfortunately, I had been scheduled to go down at 11am right after my run, despite my 6pm flight. That meant I would arrive at the airport and spend maybe 5 hours there. For those of you who have not been to the La Serena airport, there's nothing to do there. There is a small restaurant area at the top and the gate access at the bottom with a few stalls selling souvenirs. Within the gate (which you can't go in until about half an hour before the flight) there are only a few chairs and that's it. Spending 5 hours there, with only about 2 hours of sleep, would be hell. Fortunately, the staff had anticipated this. They let me use one of the dorm rooms in La Serena for several hours. My original plan had been to rest up and then work, with a possibility of walking around town. In actuality, I was so tired I fell deeply asleep and only the alarm woke me up in time. Clearly I was exhausted and I'm grateful the Observatory staff arranged for this.

El Pino (the pine tree) and the offices of Las Campanas in La Serena.

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