Alycia Weinberger – Page 4 – Extreme Wavefront Control Lab

2014B Day 31: Clio Smiled at Me

Infrared cameras are tricky beasts, forced by us ground-based astronomers to
work while bathed in background photons impinging from every direction. Clio
is also a bit on the complicated side, working as it does all the way out to 5
microns, with two camera scales (hence a movable camera lens), two filter
wheels, and various other moving parts.

During some tests of ghosts and pupil reflections that I did with Katie
yesterday, we noticed some interesting abstract shapes. Of course, the human
brain is always keen to find patterns, so I liked this image where Clio smiled
at me with a twinkle in its eye:

As a result of Clio’s smiles, we go for the Cheshire Cat smile and tend to keep our primary target to the upper left of the detector, which places the ghosts and reflections as far away as possible.

These images were taken of one of my favorite stars in the L’ filter and the wide camera, but we see the same basic patterns on stars I don’t like as much, in other filters, and in the narrow camera.

Since we’re mainly interested in science (planets, disks, etc) close to the primary star in the field, this constraint doesn’t cramp our style too much.

People always ask me why astronomers bother going to the telescope any more. Obviously, we don’t have to go to the Hubble Space Telescope (though it’d be fun). It is possible to make a telescope operate remotely. It takes a lot of money, but yes, it can be done. Ground-based telescopes face more changeable conditions (see bath of infrared photons, above) including the atmosphere (enter MagAO), and thus are even harder to automate. But to be honest, part of the joy of being an astronomer for me is collecting my own awesome data. I like the anticipation of sunset on a clear sky and the tired feeling of satisfaction at dawn. OK, I also like the sense of control.

One angst-inducing feature of taking one’s own data is having to know when to stop. We come to the telescope with lists of objects to do, usually lists that will take far longer to finish than the available time. We do on-the-fly data reduction to see how we’re doing. This leads to my, sadly proved by experience, rule, which I will here set out as Weinberger’s Law: While at the telescope, the signal-to-noise of your data will appear higher than it does when you get home.

Jared claims this isn’t true for principal component analysis reductions where
quick look reductions at the telescope have insufficient computing power. I
maintain however, that Weinberger’s Law has more to do with optimism and
impatience (get to the next target while the conditions are great!) than CPU
cycles.

We have just discovered that this is the highest MagAO run blog post EVER (for a day). It’s a good thing Clio is smiling on day 31, because there are still 8 more days of observing.

Tonight’s song was easy to choose, as it had to come from “Ghost in the Machine” by
the Police. In my opinion, Clio is female like all capable machines (see, for example, the
oevre of children’s stories by Virginia Lee Burton
Mary Ann helps Mike Mulligan, Katy rescues the town, etc.). Plus, “Cleo” is more likely to be a female name, at least in the late 19th and early 20th centuries (apparently there are no young Cleos and no baby Clios at all).

So, since Clio is a “she”, the song is “Every Little Thing She does is magic.”

2014B Day 28: Variability for Good

My blog post for tonight was inspired by the coincidence of Katie searching the online astronomical database SIMBAD for a bright star near where I wanted to point on the sky and finding “AO Men.” No, Laird and Jared haven’t been honored with entries in SIMBAD. As I said, it was coincidence. Variable stars, as they are discovered, are designated by capital letters starting with R, followed by the constellation name (or abbreviation). But there are lots of variable stars (in fact, when you get into the details with Kepler, there are hardly any stable stars, but let’s not go there right now), so after R-Z, then variable stars are called with double letters RR-ZZ and then AA-RR. So, AO Men is the 69th (or something like that; there are a lot of arcane rules of the naming, see http://en.wikipedia.org/wiki/Variable_star_designation) variable star discovered in the constellation Mensa. As I said, there are a lot of variable stars, so all the constellations I had the energy to check had an AO.

This led me to consider these stars as friends of AO:

AO Men – Unfortunately, there’s no constellation Womensa, but if we consider “men” in the sense of “humans”, Katie and Jared certainly qualify as AO Men (get it — yeomen), as they do an incredible amount of work up here to make this run a success.

Quote of the night: Jared, bragging about his hand strength — “That’s AO Men right there.”

AO Car – the little manual transmission Toyota that I drive up to the dome in when I’m too tired to hike it.

(Note: the coordinates are not exact for the named stars in the little Aladin-Lite images because of how I did the screen shots. If you want to observe these AO stars, look up your own coordinates first!)

AO Cap – the hard hats the team has to wear when working in the dome (modeled here by me in a selfie)

AO Pup – The vizcacha, of course. Sadly, I haven’t seen her on this run yet.

almost tame — A vizzy hanging out waiting for sunset

AO Cam – The wavefront sensor detector. The system has been running so smoothly that it’s been largely ignored. See — no one is in front of the AO Cam in this picture from tonight. In fact, as I was writing this, the screen saver on the computer went on.

And finally, the star as my favorite question, “What is ‘AO For‘?” Tonight, the answer is that it’s for producing awesome images of young stars so I can image their disks and planets (if they have any). Of course, the night wouldn’t be complete without a binary star (it’s not AO For, but it’s what AO is for):

Here’s one thing that doesn’t vary: MagAO is awesome.

Katie is insisting there be a song. I chose this for the lyric, “After changes upon changes
We are more or less the same.” And because I just really like Paul Simon.

2014A Day 14: Everything is Awesome

I’m very happy about how we switch between our target of interest and its point spread function (PSF) star, so I’m guest blogging about it. We want the same AO correction on both objects, even if they are slightly different magnitudes (usually we choose a slightly brighter PSF). We also want to be very efficient, of course, and change between them quickly.

Keeping these in mind, I look for a PSF that is 1) nearby on the sky, i.e. within a few degrees of the target, and 2) has a similar temperature to the target (so the wavefront sensing in visible and the IR camera still see similar brightnesses).

When we are ready to go to the PSF, it takes everyone working together to make the change efficient. We make sure the two science cameras are done integrating, and then we tell the AO operator (AOO) to “pause” the AO. This opens the loop, but saves the gains (the strength at which the AO modes are driven). Once the AOO confirms that the AO is paused, the Telescope Operator (TO) moves the Magellan guider from its park position (GPARK) to its center position (GCENTER). Once the guider is in, it occults the wavefront sensor, but we can see in the guider field of view exactly where the star was placed when it was centered on the pyramid. Since the AO wavefront sensor is off axis, the location of the star as seen by the centered guider changes with time and position on the sky, but since our PSF and target are close together, the position of the PSF should be very very close to where the target was. So, the TO marks the position of the target in the guider.

Now, the TO slews to the PSF star and brings it to the marked position on the guider. He then moves the guider out of the way, back to its park position, and voila, the PSF appears on the pyramid. Then the AOO can unpause the AO system, and we’re locked on the PSF with the same gains (level of correction) as we had on the target.

This is super efficient. From the time of our last integration on the target to our first integration on the PSF is less than 3 minutes! That is a testament to the efficiency of the Magellan TO and telescope as well as the efficiency of our teamwork on the AO pausing/restarting.

In other words, “Everything is cool when we’re part of a team.”

Which Lego character should we assign to Laird? — No, you have to keep reading, the Lego Movie soundtrack does not supply the song of the day.

We’re not just singing “Everything is Awesome” on our PSF switching. We also sing it when we’re able to stay closed loop on a star when it passes only 46.5 min from zenith. Magellan is the only Alt-Az telescope I know that tracks so well at zenith and without vibration. And Laird says MagAO is the only system that can keep the loop closed when the rotation is changing so fast. How awesome is that?

By virtue of doing my afternoon conference call from the Vizzytor Support Building, I got a good look at our sleepy friend Vizzy. An energetic relative of his (hers?) was hopping around the rocks just west of Clay as I left the dome yesterday morning.

I wish I could sleep as late into the afternoon as Vizzy.

Tonight we said <cough> goodbye </cough> to Alfio, who is headed back to Italy tomorrow (despite the efforts of the Lan Chile domestic pilots strike). Kate chose this farewell song in his honor. We trying not to let the AO system know he’s gone, since it’ll be 24 hr before we can call him with any desperate pleas for help.

And finally, for some science. Here is a cool quick data reduction complements of Kate Follette that shows the re-detection of the accreting (H-alpha bright) point source from last year’s commissioning run (HD 142527B in Close et al. 2014, ApJ ). The new H-alpha and continuum filters are working well (see yesterday’s blog post showing the differential imaging).

B is just 86 mas from A. — HD142527B imaged at H-alpha again!

Comm2 Day 14: An outsider arrives

I get to give an outsider’s perspective on the AO system as a guest blogger
tonight. It’s incredibly exciting to be here and see the AO working.

As best I can tell, the team was not intentionally showing off when just after
sunset, Alfio flattened the secondary, Gabriel our TO brought up the primary
mirror, TJ aligned CLIO’s masks and Katie was off and running for some CLIO
phase plate orientation tests on the Trapezium.

I spent the first part of the night trying to absorb how the three components
(secondary, visAO and Clio) all play nicely together. That’s 8 monitors of
information going at once. It’s mesmorizing to watch the pyramid wavefront
sensor, even if it’s just a slowed-down version of the real-time loop.

I have to admit to some dismay when I saw the bad cosmetics of the Clio
detector. Really, we’re working with that? I preserve it here so we can
reminisce about how ugly it was after it’s replaced next fall.

We all have some blemishes, it's true, but Clio has more than its share. — We all have some blemishes, it’s true, but Clio has more than its share.

Katie and TJ quickly showed me that most of the centrally located blemishes
subtracted out well. And really, once I saw that lovely diffraction limited
image on it, I (mainly) forgave it its cracks, holes and delamination.

Look at that Airy ring. You could marry someone with that.

I’m enjoying watching TJ’s scripting efforts and his insouscience in the face
of guff from the VisAO/secondary crowd. Readout and usage of the detector is
pretty efficient, and getting better with every script that TJ writes. Maybe
if I can get up to speed on running Clio, I can provide a bit of a break to
the overworked commissioning team here who have been concentrating without a
break for over a week.

The optimism in the room is delightful. The weather helps; apparently the
commissioning team believes that Las Campanas is the Lake Wobegon of observing
sites. The telescope is strong, the skies are good looking, and all the seeing
is below average.

Yes, it's warm and comfy and the wind is low, but look at the next figure. — Yes, it’s warm and comfy and the wind is low, but look at the next figure to appreciate Las Campanas / Magellan fully.

Look at that better than median seeing. — Love that seeing.

Oh, and I would be remiss if I didn’t note that we made awesome images of one of my favorite disks at not one, not two, but three wavelengths while running VisAO and Clio simultaneously. That jazzed me awake for several hours, but I have to admit that the travel fatigue finally caught up with me, and I had to head back for some sleep at about 3:15 AM. I walked down to the Lodge under a moonless clear sky, with the Milky way from horizon to horizon. The Galactic Center was rising. I actually had to look hard for Scorpius because there were so many stars that even Antares didn’t pop right out. Truly, the skies over Las Campanas are breathtakingly beautiful, so much so I almost woke up again. Almost.

Quotes from the night:

“You’re greedy, aren’t you? No, I see, you’re not greedy, you’re just spoiled” –Alycia to Jared who wanted to wait for the seeing to drop from 0.6 to 0.3″ before he did his favorite target.

“VisAO is going to melt” — Laird (you may have heard about its hot filter)