Sunday, January 3, 2016

Epic Seeing

As an astronomer, I had to learn to "let it go" when it comes to the weather. It is completely out of my control, and sometimes I am lucky, and sometimes I am not. I had a discussion at dinner a few nights ago with the observer on the other telescope (Baade), Dan Milisavljevic, about the risks and rewards of ground-based observing. He commented on how curious it must be to non-observers that we spend so much time and money and energy on an activity with such inherent, known risk. Las Campanas is one of the best sites to observe in the world, but there are still nights lost to weather -- last August I lost two nights, and friends of mine have lost more. But my comment was, that's part of what makes observing exciting, especially classical observing (where the observer themselves goes to the telescope, versus queue observing, when someone else does your observations for you). There is an unpredictable aspect to it, and you have to be ready to think on your feet to adapt to whatever the weather brings. When the weather is bad, it is really disappointing, and certainly projects and science suffers. But when the weather is good, it is like magic. 

As I post this, I'm in the middle of a 13-night PFS (Planet Finding Spectrograph) run with Steven Shectman. Observing at Magellan with Steve is a special treat, because he designed and built the telescopes (with the help of many others). Steve knows all the ins and outs of the structure, the site, the mirrors, the telescope computers and software, the staff, and most of the instruments. He was and is an invaluable resource to Las Campanas, and really to our community overall. It is a privilege to know and work with him. It's also really fun. 

So, it is like a sundae with a cherry on top when I get to observe with Steve and we have good weather. And this run, so far, we've had the longest stretch of good weather I have ever experienced at LCO. Minus a few clouds last night that moved in and out quickly, we have had clear, calm skies with remarkably good seeing (very little turbulence in the atmosphere, so the starlight is better concentrated into our narrow slit). I've written about good seeing before, but that was only over two nights. We're on our sixth night of near-pristine or pristine seeing; for calibration, 0.5'' seeing is considering very good, and rare at most other observatories. A few nights ago (New Year's Eve, actually), I took this screen shot at the end of the night...and added some embellishment: 

This shows the seeing as a function of time, increasing to the right. The telescope we're using is in red. At the end of the night, we had several bouts of < 0.5'' seeing. Epic! (Also note that we, in red, won the seeing battle with Baade that night. I think so far we are winning 4 nights to 1; we'll see how tonight shakes out.)

But tonight, tonight is really magic. Take a look at the same plot from tonight so far:

See how much we are below the 0.5'' line?! I swear I saw 0.39'' on the seeing monitor, and we've had consistently 0.4-0.45'' seeing for over an hour. This means that we are more easily able to observe very faint stars, which will make our colleagues working on HAT-South and K2 transiting planet follow-up very happy. More about that soon.

Update at the end of the night...


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