In a typical year, July and August bring monsoon rains to Arizona and New Mexico. The rain is much needed in the desert, but it does mean poor observing conditions for most of those two months. Because of that, the observatory typically shuts down its major telescopes for ongoing maintenance and upgrades that help keep them state of the art.
Those of us who work principally at night, often get a more relaxed schedule, which enables us to take vacation time. When we’re at work, we often get a chance to lend a hand on projects around the observatory. This past week, I worked during the daytime, helping with a couple of projects at the WIYN 3.5-meter telescope. One of those projects was cleaning, tuning, and testing the actuator control cards on the back of the WIYN telescope.
Here you see the back of the WIYN 3.5-meter telescope. Each of those disks at the back are attached to a motor and a rod, which deform the telescope’s primary mirror so it has the optimal shape, no matter where it’s pointed in the sky. With time, the electronics in each of those actuators becomes less reliable.
So, for example, the WIYN primary mirror weighs about 4200 pounds. When working properly, the actuators should measure that weight pretty accurately. However, with wear and tear, they reached a point where they were measuring the weight as 4570 pounds. As I write this, we’ve tuned about about one third of the cards and now the weight is reading 4370 pounds, much closer and an indication that we’re doing much-needed work. Here’s one of the control cards in its test bench setup.
Another project I helped with this week was upgrading the drives for the filter arms on the One-Degree Imager at WIYN. In essence, the whole objective of having a camera on a telescope is to accurately measure the amount of light coming into it from distant stars and galaxies. However, visible light is made up of all the colors of the rainbow. Red light, blue light, and violet light are all jumbled together. So, the best way for us to measure light accurately is to take black-and-white pictures with colored filters in front that allow light of precise frequencies to pass through.
The One-Degree Imager has filters that are approximately one-foot by one-foot square. It takes a lot of force to move those pieces of glass and hold them rigidly in place.
In the photo on the left, you’re looking down on the filter arms. The filter arms used to be held in place by a series of gears. However, the force required to move those arms was so great, the gears were literally grinding themselves to dust. So the gear system has been replaced by a system which utilizes a chain drive like that you might find in a motorcycle! You can see the chain on the bottom of the photo. I’m looking forward to the new observing season when we get to use this new filter drive system. It promises to move and hold the filters much better than the old system.
Another project that’s moving forward is the Extreme Position Doppler Spectrometer which NASA is contracting for the WIYN telescope in order to support space missions searching for planets around other stars. This week, I was asked if I would provide input into how to practically operate this device. It sounds like I’ll learn more this autumn, but I’m looking forward to the challenge and hoping I’ll have something good to contribute which will both help achieve the mission objectives and make it a user-friendly instrument.
In the meantime, I have not forgotten my literary endeavors. I just finished editing a four-short story collection called Sugar Time written by Joy V. Smith. Hadrosaur Productions published an audio book edition some years ago, but this will be an ebook and chapbook containing the four original stories with new cover art by Laura Givens. Look for more details in next week’s blog post.
Also, if you live in New Orleans or will be visiting on the weekend of August 22, please drop by Boutique du Vampyre in the French Quarter between 3 and 6pm, where I’ll be signing copies of Vampires of the Scarlet Order and Dragon’s Fall: Rise of the Scarlet Order.
David Lee Summers' Web Journal 
Great blog and one I’ll have to reread! I just found out about Modified Newtonian Dynamics. Trying to understand the concept (the math, well, that’s nit gonna happen). What are your thoughts on that?
Thank you! Glad you enjoyed this glimpse into my day job. It’s been a while since I’ve thought about Modified Newtonian Dymanics. The goal was to explain galaxy rotation profiles without the use of dark matter — which is kind of appealing. As I understand, the problem is that it doesn’t really succeed at eliminating the need for dark matter, because it doesn’t do well predicting globular cluster dispersion profiles or temperature profiles of galaxy clusters. Also, it gets to be pretty complicated to make it work for non-relativistic, small scale Newtonian dynamics like we see around us all the time. That said, I’m hardly an expert — this is much more theoretical physics than I use in my day-to-day observational world. 🙂
OK. I just heard of it and wondered if it played any role in your astronomical work. That said, how certain are estimations/figures of mass, energy, light and so on made by astronomers for far distant observed objects. How much does gravity and other forces disrupt/alter outcomes?
What you’ve asked could almost be the considered the central questions of astronomy! Basically, the two most important forces we deal with are gravity and something that has the ominous name “dark energy.” It’s called that because we don’t know what it is — all we know is that it appears to cause galaxies to accelerate as the universe expands. Getting more data to get a handle on what it is, is perhaps one of the most important things we’ll be doing at the Kitt Peak 4-meter over the next decade or so.
What we know well is the chemical signatures of all elements as they manifest in the spectra of light. This is a chemistry lab experiment that can be done right here on Earth. The faster something is moving away from us, the more that characteristic chemical signature is shifted to the red end of the spectrum — that’s what we call redshift. That’s the fundamental observation we make on distant objects. It tells us what things are made of — we get the most abundant elements to high accuracy. By using those same techniques on more nearby objects, where we can also make more direct observations, we can bootstrap the techniques to get good distances, luminosities, and so forth for more distant objects. Of course, the more distant something is, the more uncertain the numbers are. And they rely on something called the cosmological constant, which astronomers are in pretty good agreement right now, but who knows how dark energy observations will change all that.
I feel like I’m skimming over stuff here, but yeah, yours are essentially THE questions. Neil deGrasse Tyson did a pretty good overview of a lot of this stuff in the series Cosmos: A Spacetime Odyssey. If you haven’t seen it, the episode “Hiding in the Light” gives a pretty good explanation of the fundamentals behind all this.
Thank you sir. I had a feeling very distant objects would have, to an extent, unreliable calculations. But sometimes I hear scientists speaking things with such certainty I wonder, “how can he be so sure? It’s so far!”
This clears things up, and makes me interested in redshifting. Keep up the good work!
I guess I would say less “unreliable” and more “model dependent.” Also, when you go to the scientific literature, you’ll find these results presented with error bars, but when you see these things reported in the press, that kind of info is left out — often just due to keeping the story brief.
Furthermore, a lot depends on what you mean by “distant.” When you consider it just took one of our fastest spacecraft 10 years to get to Pluto, which is only about 10 or so light hours away, and the closest star is some 4.5 light years away! I think it’s fair to say we actually know a surprising amount about the most distant objects in the universe.
That said, my point is, things like masses, luminosity and chemistry of stars in our own galaxy can be gained pretty darned accurately because we have such a large sample size of stars and have a good handle on how gravity works on the scales of stellar systems. This allows us to give pretty good numbers for things like sizes of planets. Again, there are error bars depending on assumptions, but on the scale of our galaxy and our local group of galaxies, those error bars should be fairly low.
At any rate, I think it’s fair to say much as we know, there’s still a LOT to learn. 🙂