General – Page 8 – Extreme Wavefront Control Lab

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.

I <3 Pupil Plane — 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 - ASM slot and telescope spiders — 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:

Airy = abs(FT(pupil))^2. — 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:

Fourier optics rocks — 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:

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: $Diffraction spikes and Airy rings$ 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.

For Alan

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!

(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:

by KT — Power cords protector, standing around the plugs imaged above

NAS Fitcheck Day 3: Cold, Pressurized, and Telecentric

The weather has taken a turn for the worse at LCO. It is currently 1.8C and blowing at 32.7 mph. And getting colder.

Speaking of cold, we installed the new liquid cooling system in the W-Unit today.

Here, hold this. — Jared and Laird installing the brass cold-plates on our CCDs.

This again? — Jason getting ready to install the shutter. Jason first assembled the shutter heatsink and mounting system nearly 2 years ago.

My Precious. — Jared checking the shutter mounting. It is a tight fit, and we don't want any metal-metal contact because the shutter vibrates. A lot.

News team, assemble! — The team at work on the NAS, under appropriate supervision.

A real Viscacha nest. — The finished product.

Hold your breath. — The test gauge for the CCD cooling system.

The other big accomplishment in world of the NAS today was Laird installing the Telecentric Lens. This almost flat lens lets us work off-axis, away from the guide star.

See the tele center? — View past the cube, through the new telecentric lens. That's L1 there.

A happy AO operator . . . — After installing new glass, we checked the system. Everything looks great - the wavefront is flat and our i' PSF is 3.2 pixels. Click for more pixels.

We also got some time in the dome, and did a little work on the Clay telescope. The vane-end trays are installed, and the leak preventing solenoid valve was plumbed and tested.

High up. — Jason and Juan working on the solenoid.

Don't drop anything. — Installing the vane end trays.

This hawk was hanging out over the observatory at lunch today.

Hawkish — A hawk over Magellan. Click for full wingspan.

Tonight’s pretty pictures are from Alan Uomoto, who spent some time messing with his camera’s settings today.

Pretty, unless you're an astronomer. — The beginning of the weather. Note the top of the fog in the valley below. Click for bigger.

Magellan casts a wide shadow. — A panoramic view of the hotel and Las Campanas itself. Click for more awesome.

Days without a motherboard failure: 2

NAS Fitcheck Day -1: Back To Work

MagAO is back at LCO. Jared arrived yesterday (Day -1 on the schedule) to begin preparing for a “fitcheck” where we will bolt the NAS to the telescope and test our communications and plumbing. The NAS (=Nasmyth Assembly because it goes on a Nasmyth port of the telescope) is the big black ring that holds our cameras.

The trip to the mountain from La Serena had some excitement. An accident on the highway caused a long traffic jam, so we followed some locals and took an offroad shortcut.

Up The Side — We followed this truck on the "alternative" route around the traffic jam.

Long Wait — Looking back at the backed up highway after we'd circumvented the mess.

Everything is just how we left it, waiting for us to come back.

ASM — The secondary in the clean room, wrapped up to keep dust out.

Never Disappoints — A familiar view. Still gorgeous.

Cleared To Ship!

After our pre-ship review, we had a few things to fix – the only difficult one was a misbehaving actuator in the ASM. These have all been dealt with, and after a final review by the director we today received permission to ship the Magellan AO system to Chile.

LCO here we come!

Some packing pictures courtesy of Carmelo Arcidiacono: