Blog

Things are winding down here.

Today we did a big set of readout noise measurements on both of our cameras. We did a preliminary set a few days ago to make sure shipping went okay, but now that we are pretty much fully integrated we did it again. We’re really happy with the results – it looks like both cameras are performing as well as they ever have. Maybe the most important result is that there is no sign of any coupling between the cameras or any interaction with other components of the system. That means that no matter what I turn on or off while taking data the noise doesn’t change. Great news!

We routed our cooling hoses around the NAS, making sure they all fit. We won’t actually run glycol through them until our next trip.

Marco already told us about the final steps in ASM testing, and lots of other odds and ends were taken care of in WFS land too. But that’s enough work for today.

Today’s quote: “I can’t tell if you’re here to do zoology or adaptive optics.” (Glenn Eychaner)

This morning Amanda Zangari, who is using the Clay telescope, was walking down after sunrise and spotted a Vizcacha outside the Astronomer Support Building. In exchange for a tour of the AO system today, she sent me these pictures to post.

Now that we know they’re around, I think it’s official: VisAO has a mascot.

And I managed to catch the Magellan telescopes right at sunset tonight.

Tip for users of pyramid wavefront sensors: you are not very sensitive to focus with a large modulation amplitude. For MagAO in particular, you have to get amplitude down to ~.1 milliradians before you really have any z-stage resolution.

Tip for users of the VisAO camera: there is a huge factor (it appears to be about eight) between z-stage motion and VisAO focus stage motion. So failure to heed the above PWFS tip will cause you to tear your camera apart several times in one day trying to find why your focus position shifted. You will feel very dumb later.

So that’s the story of Laird and Jared’s day. Because we forgot these two things, we were completely and totally baffled by the results we were getting when running focus tests on our camera. Since we replaced our gimbal mirror (the motorized mirror that lets us steer stars around our detector) we naturally assumed that was the problem. We even made up a bunch of reasons why it could be and proceeded to apply made up solutions. But in the end, we just hadn’t been careful enough with focusing on the pyramid, and so our numbers were meaningless and our time wasted. The good news, I guess, is that we earned a bunch of intuition for how our stuff works. When life gives you lemons . . .

This story started last night, when we figured out how to tighten the beam splitter wheel – making it much more repeatable. This changed the angle of our beam slightly, causing us to adjust our gimbal angle a little.

See Katie’s post here for a demo on why we’re so obsessed with our gimbal and beamsplitter. Those two devices need to be reliable and repeatable for us to efficiently acquire the stars we use to measure turbulence. They also need to be as free of vibrations as possible for VisAO science operations.

All this visible light focusing meant working with the lights off in the lab. That didn’t stop the ASM testing.

An argument broke out at lunch today over how many days we’ve actually been here. Luckily we have a blog, so we just looked it up.

As the Guanaco noticed, Mario and Frederico have left us after more than pulling their weight. They took the early bus to La Serena.

Now that the TSS is fixed, we moved on to mounting our windscreen. This is just a metal ring that encircles the bottom of the ASM to protect the shell from high wind. We also removed a set of shims from the mounting system.

In the afternoon Laird spent some time perfecting the routing of cables to the W-Unit. This is a hard problem – the whole thing translates in 3 dimensions, and has to be able to turn upside down, and cables tugging on optics generally ruins nights.

Today’s quote: “You know Laird, you need to seriously think about hiring an exorcist.” (Armando Riccardi, commenting on Jared’s project long bad luck with electronics).