President Michelle Bachelet addressing those celebrating the groundbreaking event for the GMT on the windy evening of November 11th.
President of the Republic of Chile Highlight of GMT Groundbreaking
Category: General
GMT Groundbreaking
On November 11th, I had the great pleasure of attending the Groundbreaking Ceremony for the GMT. It was a very windy, cold, but happy occasion. I’ll be posting a more complete update in the next 24 hours, including hopefully some of the photos that I was able to take during the celebrations. The event was well attended, including wise and often humorous remarks by the ambassadors to Chile from Australia, South Korea, and the United States. The President of the Republic of Chile, Michelle Bachelet, was the keynote speaker. Everyone working to build GMTO (the GMTO staff, the many people from all of the partners involved, including the talented women and men of Steward Observatory and the Richard F. Caris Mirror Lab) should be very pleased to see the project reach this milestone.
Fortunately for the MAGAO team, the more than 150 people that were visiting the mountain yesterday have now left, leaving hopefully enough room for you to work and sleep during your upcoming long observing block!
New Results In The Chamaeleon
Now that the MagAO team has (mostly) recovered from our epic 6 week stay at LCO, we are turning our attention to processing all of the great data we’ve been taking. We’re also happy to announce two new publications based on MagAO data which have been accepted to the Astrophysical Journal, both of which looked at stars in the constellation Chamaeleon.
Ya-Lin Wu has been studying the young star CT Cha with VisAO. You can read about his results here.
Steph Sallum used Clio2, in combination with some other instruments, and used a resolution-boosting technique called non-redundant masking to take a look at T Cha. You can find out about her results here.
We have a bunch of other papers in the works, and we’re already starting to plan for our next run, which starts May 3rd. Stay tuned!
Comm2 Day 17: Calibrating Clio while clouded out
We were clouded out tonight:
Also, a truck on the highway had an accident, which closed the highway, so the new turno couldn’t get here so the day crew had to also be the TO’s at night. We’ve been away from home for ~3 weeks and everyone is tired, but we stayed up all night in the control room working.
So, instead, I’ve been working on reducing my data, which includes determining various necessary calibrations for Clio. One important correction needed for high-contrast photometry is calibrating the linearity of the detector. To do this calibration, I took a set of measurements of increasing integration time, and determined the counts per itime:
I then fit various functional forms to the data until I found the best calibration of the linearity is a third-order polynomial that must be applied to pixels with counts above ~27,000 DN in the raw images, giving the result here:
Note that the data cannot be well-corrected above ~45,000–52,000 DN (depending on your tolerance for photometric error), and these values should be considered saturated in the raw images. I apply the calibration through an IDL function I wrote called “linearize_clio2.pro”. This is going onto the Clio observer’s manual.
Jared and I are working on astrometry, comparing Clio and VisAO measurements and exploiting our capabilities for boot-strapping: Clio has a wider field (up to ~30”) and can get a longer lever-arm on astrometric measurements, but VisAO has a finer pixel scale (~8mas) and a tighter PSF and can get precision astrometry on close companions. We are starting by verifying that we both get the same measurements for the locations of stars in the Trapezium cluster. To do this, I look at our Trapezium images and identify which star is which, then I compare the positions I measure to the positions measured by an earlier author. Here’s an illustration:
I’ve measured the plate scale in both cameras and various filters, as well as the rotation offset to orient the images with north-up, which I’ve written in the IDL function “derot_clio.pro”. We’re working on a code repository for these data-reduction utilities that we’re calibrating on these commissioning runs.
In fact, Clio has two cameras, a wide and a narrow camera. Here is a comparison of the fields of view, including an illustration of the overlap:
VisAO’s field of view is similar to Clio’s narrow camera along the short direction (8” by 8”).
Finally, I’ve been having a bit of fun experimenting with the APP coronagraphs that I want to use for following up GPI planets:
Well, it’s been a long night, good morning!
MagAO pupils and Fourier optics
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.
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:
Since we know what the pupil looks like, we can create simulated images of the focal plane by taking the Fourier transform modulus squared:
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:
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. Summary:
Top: ASM slot + telescope spiders pupil image and mask. Bottom: Clio cold stop image + pupil mask. 
Top: ASM slot + telescope spiders PSF. Bottom: Clio cold stop PSF. The two simulated PSFs look very similar, and diffraction off the spiders and slot has a very minimal effect compared to the Airy rings.