Thursday, February 8, 2018

PFS Upgrades Series, Day 15: El Final

This is part of a series of posts about upgrading an instrument at Las Campanas Observatory. If you want to start at the beginning, it's here.

So....this happened last night.

As in, the entire night were were closed due to high humidity. Boo. But upon leaving the telescope around 5 am this morning, everything was damp and drippy, so I have no problem with the telescope operator's decision. It was just a bit of a fizzle end to our awesome two+ weeks here at LCO working on PFS. 

Per usual, I started with a focus test, to see if it had changed since the night before. Since the instrument was nearing its ideal temperature, I expected little change in the focus value, and actually found the best focus to be the same as the previous night. We took some images to use in a linearity test -- when does the relationship between incident light and recorded signal become non-linear and thus BAD? -- which Jeff started running through an old IRAF script used with the MIKE instrument. We also figured out that the images we took last night (like in the picture I showed, with the red on the screen) actually were *not* fully saturated, so we did the same test over again, changing the CCD voltages to make sure the saturation limit did not change much between the different voltage settings. It did not change enough to make us want to go back to the voltage setting with the wonky bias. I got a nice explanation from Steve about what A_HIGH and A_LOW mean -- basically they are the top and bottom voltage values of a "bucket" that moves electrons along the detector for readout. Steve drew a diagram almost exactly like the "clocking diagram" here. I learned about this in graduate school, but hadn't really applied it to real life measurements/data until now. Knowledge! 

Then the rest of the night was mostly spent watching for the humidity to drop, which it did a little, to something like 77.5%, but never low enough to open to dome. Sigh. I did take the time to read all about the new TRAPPIST-1 results, though! I also sent all the data to Paul Butler, who replied this morning that he'd received it and would work on a reduction soon. We will eagerly await those results.

After getting a few hours of sleep, I got up this afternoon to tour the Giant Magellan Telescope site, which is one peak over from LCO. Funny enough, that peak is actually Las Campanas peak. The GMT site is leveled off and has chalk designating where the dome and mirror base will go -- GMT will be made of seven 8.4m mirrors, built at my grad school alma mater the University of Arizona -- as well as the auxiliary building where mirror coating will happen and an extra mirror will be stored. We also got a tour of the "casino" (kitchen and dining hall) and recreation facilities for the folks living and working at the site now. It's still hard for me to picture everything coming together, but I still got excited visiting the site. 

Each of those circles represents the footprint of a 8.4m mirror. 
LCO from GMT site. Iiiiiity bitty telescopes.
Above: Mosaic in the recreation area at GMT.

Below: Leon ringing the "las campanas", some of the ground-breaking rocks from the GMT site.

But for now, I'm perfectly delighted to work at LCO and use the telescopes here. Part of me is ready to go home, but part of me could stay here forever. Tomorrow Jeff and I go back to the US, while Christoph and Steve are staying a few more nights to observe with MIKE, another high resolution spectrograph that Steve built. Jeff and Steve will be back here in March to install a new dewar in PFS and hopefully something to control the icicle formation and melting that has been happening in the tube were we fill the dewar with nitrogen. At some point we'll install fibers and a pupil slicer, I hope by the 2018B semester. I won't be back until May for more PFS observing, when, I realized, it will be my 10 year anniversary of coming to Magellan! My first visit was right after I graduated college in 2008, when I was finishing up an internship at Carnegie DTM with Alycia Weinberger, who continues to be a great mentor and friend. So many good memories here! 

I'll sign off with some pretty pictures. :)

Hawk friends saying goodnight last night. 
I always think of the Stairs of Cirith Ungol when I go up and down these. I don't know why, they are happy stairs, not scary stairs!
The previous photo was look down the stairs after climbing them, this photo is what you see when you reach the top. See, happy stairs! From left to right, Clay Telescope (Magellan II), auxiliary building, Baade Telescope (Magellan I).
Looks like a good night tonight! I will be spending it sleeping, but hopefully the humidity stays low for the observers.

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