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Before we tell you our big results for the night… let’s look at some happenings up and down the mountain!

Here are Enrico and Alfio waiting for a ride up to the telescope:

Armando departed on Saturday, and now Derek and Marco have also gone down the mountain.

Derek saw a horse on his way down the mountain.  We’ve seen them before on this blog!

Coming up … REAL on-sky results!!!

We passed a big milestone today with the ASM working in closed loop with 400 modes at 1 kHz (the most complex AO mode)!  This 400 mode interaction matrix has been made possible by the excellent trouble shooting from our friends at Arcetri Observatory, Simone, Enrico, Alfio, Armando and Marco!

It was such an exciting event that Alan Uomoto made a movie:

How did this happen?  Well, yesterday the AO loop was struggling to close on the bumps we were referring to as Viscachas:

When the loop tried to close on this, we would get a higher and higher unstable patch of actuators trying to correct it:

So Simone and Enrico figured out that we were actually getting cross-talk from the Pyramid, because the phase bump was so high.  This is similar to a quad-cell Shack-Hartmann without a guard band, where a subpupil may wander into an adjacent subaperture.  Here is Simone’s drawing where he works out the solution:

So the solution is kinda a hack, whereby we applied a negative sign to the interaction matrix for that patch — and the bump and the viscacha disappeared!

And so tonight we were able to close the loop with our new interaction matrix, and get a nice flat wavefront!

New arrivals today: T.J. Rodigas (Steward) and Runa Briguglio (Arcetri).

Sorry for the tardiness of this post. The internet was down on the mountain when the night shift went to bed this morning. The day was a struggle, but we finally got at least something working, and then did some testing through the night.

The issue was a feature in our pupil which Simone has dubbed the Viscacha.

We tried several things. One quick and dirty modification was to remove the field stop for the Pyramid. Simone and Enrico climbed into the NAS to do this – after first convincing Laird that this was a good idea.

The day shift ended with a somewhat working 200 mode interaction matrix. So the night shift did some closed loop testing.

Things are hopeful. With only 200 modes we have a fairly high Strehl ratio PSF. The problem is keeping it stable. These two videos, taken with the VisAO CCD 47 at 32 fps, show this.

Youtube noted that my image was shaky, and asked if I wanted to fix it. F*&!$^ you Google. Here’s the same data set, but keeping only the best 5% of the images (Lucky imaging style).

After breakfast Laird reduced this data by “shifting and adding”. Here’s what our images will look like soon:

To try to control the vibrations that even Google noticed we put the Clio rack on some foam pads. This improved the power spectrum, at least removing the ~2 Hz spike.

Quotes:

Simone: “Laird, take a seat. You want to take your seat. I think we need to remove the Pyramid . . . field stop.”

Tyson: “Why don’t you just say you’re a carnivore plus vegetables and cheese.”

Laird: “I thought you were trying to take the frisbee away.” (To Phil, after realizing that Phil was playing frisbee with grad students and the post-doc.)
Phil: “I was just trying to help them meet their 100 hours for the week.”

Simone, on the viscahcha in the PWFS pupil images:
“The viscacha again!”
“There is a clear viscacha.”
“It is not a dynamic viscacha, it is a static viscacha.”

Laird: “It looks like a viscacha that’s been run over by a car.”
Simone: “Yes, but it’s still a viscacha!”

Laird: “I’d really like a headless, tail-less viscacha.”

Here’s a riddle for all you AO fans out there:

What aberration can be sensed but not corrected?

Usually an AO system has the opposite problem: There are aberrations you can correct but not measure.  And of course, there are all sorts of aberrations you can neither measure nor correct, like the very highest spatial frequencies. (And if you don’t have enough stroke, you can saturate your attempt to correct an aberration — but that wasn’t the case today.)

But today while we were making our interaction matrices, we found we had 3 high spatial frequency dots in our pupil images (a couple times the size of an actuator) and we spent some time trying to track down whether they were phase or amplitude, and whether it was a dirty optic, scattered light, or misalignment.

Jared had to power-cycle the CRO controller, and so he and Armando went up on the scissor lift to check if the CRO was in the right position and to inspect the optics.

When we closed the loop, these “dots” could not be corrected.  We tried shifting some optics to see if we could move the spots, and we concluded they weren’t an amplitude error (too bright).  Finally, we tried setting the ASM back to an older flat shape — and the dots disappeared!  This means that these phase errors were somehow introduced to the system at the time we were calibrating the interaction matrices.  So then when we closed the loop, we were driving toward that shape — not toward a true flat.

So the answer to the riddle is, the shape you can measure but not correct is an error in your null!

Now that we’ve solved the riddle, tomorrow we’ll re-do our interaction matrices with a flatter null.

Yesterday:

Simone: “Hey, I think we should try taking the pyramid out.”
Laird: “No.”
Armando: “No.”
Phil: “No.”
Jared: “No.”
Katie: “What? Is he serious???”

Today:

Laird: “Hey, maybe we should try taking the pyramid out.”
Simone: “No.  The last thing we want to do is take the pyramid out!”

Our CRO is a very fast f/1 optic, and our ASM makes an f/16 beam. So motions of the CRO are amplified by a factor of 16 in our focal planes. We can see this on the VisAO CCD47 as a dancing image due to small mechanical vibrations of the telescope.

The MagAO project is adding a little bit to the vibrations of the telescope, mainly with two cooling pumps. One pump circulates glycol for our CCDs and the Shutter, and the other keeps Clio2 cold. With the 16x CRO amplification, we really see the impact of these pumps. We recorded 60 sec time series of the CCD47 operating at 32Hz in a 64×64 subarray mode. Here are the results:

With both pumps off:

With the Clio2 pump off, and the CCD pump on:

With the Clio2 pump on, and the CCD pump off:

We are actually very happy with the vibration performance of the system attached to Clay. Taking into account the factor of 16 for the CRO reflection, we expect to have only a few milli-arcsec of jitter when we observe actual stars. We have also taken measurements with our internal artificial star without the CRO and confirmed this. Good news, especially for VisAO.

Another experiment we conducted was having the PI bounce around the control room. He has a noticeable effect.