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:
Unnormalized power spectrum of the x position of the VisAO image position. Note that I'm being lazy and not fully normalizing the PSD. With both pumps off, we had an rms jitter of 2.2 pixels.
With the Clio2 pump off, and the CCD pump on:
Here we see more white noise, but no strong resonances and the image is fairly stable by eye. Rms jitter was 5.4 pixels.
With the Clio2 pump on, and the CCD pump off:
The Clio2 pump excites a ~2.3 Hz resonance. We think this is due to the rack holding the pump sitting on a beam connected directly to the telescope. Rms jitter in this configuration was 9.5 pixels
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.
Time series of the VisAO centroid x position, with some input from the PI.
Today we are going to explore the MagAO pupils and their corresponding transforms in the image plane, courtesy of Fourier optics.
So let’s have a look at the pupil. Here is a photo of the ASM, taken with a digital camera. This was from before Clio was mounted, so that we just stood on the Nasmyth platform and put the digital camera where Clio is now. The light source is the sky, and the light path is primary + secondary + tertiary.
ASM image, from before Clio was mounted. You can see bird poop on the tertiary, a splotch at about 11:00 in this image, and the lollipop-shaped "slot" is at 9:00.
The main features of the pupil are the outer diameter of the mirror, the inner diameter of the secondary obscuration, the support spiders holding up the secondary, and the slot. Here, then, is the pupil mask:
Pupil mask
Since we know what the pupil looks like, we can create simulated images of the focal plane by taking the Fourier transform modulus squared:
What the PSF will look like in the image plane (log scale)
If we really stretch the color table, you can see the diffraction off the spiders, but it is not a big effect. Also, I couldn’t find the diffraction off the slot, so it is negligible:
Stretching the color table to saturate the inner part of the PSF allows you to see the diffraction spikes off the spiders, but they are very faint
Now, Clio is an infrared camera, going out to 5 um, and so it has its own pupil mask, a cold stop. So let’s look at the pupil through Clio, by taking a pupil image (which we did after Clio was mounted). Here is an image of the pupil plane through the whole system, taken with Clio by putting in a powered lens to the focal plane to make a pupil image:
Clio pupil image, 3.4 um
It’s pretty cool because you can see the 2 spiders holding up the secondary obscuration on the cold stop, but you can also see the 4 telescope spiders and the ASM slot! Here’s just the Clio cold stop pupil mask:
Pupil mask - Clio cold stop
And here is its Fourier-transform-modulus-squared: The simulated PSF:
Simulated PSF for Clio cold stop (log scale). Diffraction off the spiders is a little bit visible here, since they are slightly wider than the telescope spiders.
And here is the zoomed-out, saturated version so that you can better see the diffraction spikes:
Clio cold stop PSF -- scaled to bring out the diffraction spikes.
Happy Thanksgiving! I am thankful for clear skies, low winds, and contactless continuous facesheets.
To celebrate thanksgiving I gave my family a virtual tour of the Clay control room. Meanwhile, the Arcetri team was busy taking interaction matrices.
We are employing fine Italian craftsmanship to obtain the interaction matrices for our AO system, using the “penina” internal light source (an artifical star) and the CRO retro-reflector. These are crucial calibrations for the feedback loop to create the desired shapes on the ASM.
Alfio gestures at the pupil images making up the interaction matricesLaird, Alfio, Simone, and Enrico contemplate our pupils.
There were a few issues having to do with the slaved actuators in the unilluminated part of the pupil, so we haven’t finished the interaction matrices yet — there’s more alignment that needs to be checked first.
We are looking carefully at the pupil to see if the CRO is aligned properly with the ASM. So let’s have a look at the pupil. The “lollipop” is the slot that was cut out to keep a crack in the ASM from spreading. You can see it in the lower center of the ASM in each picture in this collage. There is also bird poop on the tertiary — it’s the splotch in the upper right image, at about 8:00. More on the pupil images tomorrow.
The lollipop-shaped slot can be seen at lower center (6:00) of the ASM in each of these 4 images. Bird poop on the tertiary is at about 8:00 in the upper right image.
Heard at LCO today:
“We have three telescope operators? Just for Clay?” -Laird
“No. Just for you!” -Povilas
“If you don’t know which way is which, we’ll just drill two holes!” – Pato
“It’s the bird poop.” – Laird
“So we use the bird poop fiducial?” – Phil
(a helpful bird, which might actually live in the dome, gave us a nice way to figure out which way is up in our images)
“Alfio has a segmentation fault?” – Jared
“It’s not me, it’s IDL!” – Alfio
“A pupil only a mother could love.” – Laird
“In Italy we say, Every cockroach is loved by its mother.” – Alfio
“All the cockroaches are loved by their various mothers.” – Kids
There was no turkey today, but we tried to keep up some Thanksgiving traditions:
The Las Campanas Thanksgiving kids table. No grown ups allowed.
MagAO’s official food blogger (Derek) grabbed a shot of our turkey substitute:
We had a really good fish for dinner.
We are all thankful for the 4-course meals, 3 times a day… as well as the plethora of snacks found in every building!
I am thankful for the ubiquitous and well-organized snacks at LCO!It's a nightly ritual to watch the sunset from the catwalk that joins the telescopes. Unless you are busy aligning an AO system . . .Tonight's sunset.Today's Vizcacha
Alan Uomoto has been teaching us about the power supply at LCO. Rather than calling it clean and dirty, the actual difference between the different circuitry is whether they go direct (white outlets) or through an un-interuptable power supply (UPS) (orange outlets). Alan, this one’s for you!
Before AlanAfter Alan
(And — despite how it looks from the outlets — we really are in Chile! The observatory is highly USA-compatible. I haven’t even used my plug adaptor yet!)
Update: And here is the MagAO-certified power protector I made to keep people from stepping on the plugs and cords above:
Power cords protector, standing around the plugs imaged above
Today was a busy day, and we began splitting MagAO’ers into day and night crew. See Derek’s awesome post for the bulk of the day’s tasks: aligning the CRO and ASM.
The next major happening was mounting Clio to the NAS. Even though we didn’t play the theme from Top Gunas we did it (sorry Phil!), it was an exciting moment. This is the first time our infrared camera officially met our optical camera and our AO system! They are together at the telescope at last!
Clio, VisAO, W-unit, Nas, ASM, Clay: So happy together!
Here’s how it happened:
Removing Clio from the support cart with the crane — under PI Phil's watchful careAttaching Clio to the NAS ring — under Phil's watchful careClio at the Nas, flanked by Phil and KatieLeft: Phil and Clio instrument. Right: Clio electronics rack and Phil.
Heave-ho: Shimming Clio to align the cold stopsHow's it look, Phil?
LCO crew were busy as always, making everything work smoothly for the run. Here, Mauricio brings up LN2 to fill Clio’s dewar, and Pato optimizes the PID loop that rotates the Nas while the telescope tracks and slews:
Mauricio brings up LN2 to the Nas platform to fill the Clio dewarPato feels for vibrations as he optimizes the PID loop tracking and slewing the Nas rotater
Quotes:
Alfio: “What is this mirror cover?”
Laird: “Oh you’re so cute Alfio.”
Phil: “I don’t lean on Clio.”
Phil: “Used to be, we only had 1 actuator.”
Povilas: “Can 14 mm be considered a shim? That’s more like a structural member.”
Simone has a key to Galileo's house.
Katie: “Hey Jared, how’s it going with the CRO?”
Jared: “I dunno. It’s all in Italian.”
Jared: “The number of Illuminati asking me questions is daunting.” (That would be Simone Esposito himself, as well as suspected members Laird, Phil, and Armando — see our paper for more info.)
Armandino
Jared: “I’m pretty sure I would throw myself off the catwalk if Armando thought it would help.“
