Date: March 17, 2011
Title: The New Mosaic Imager at Kitt Peak
Podcasters: Dr. Steve B. Howell & Rob Sparks
Organization: National Optical Astronomy Observatory
– http://www.noao.edu & http://twitter.com/#!/NOAONorth
Description: Astronomers are constantly developing new technology to improve their ability to see fainter objects and learn more about the cosmos. The National Optical Astronomy Observatory recently upgraded the Mosaic imager. In this podcast, Steve Howell discusses the process of upgrading the camera and the new science abilities it will bring to the telescopes on Kitt Peak.
Bios: Dr. Steve B. Howell is a staff member of the National Observatories located in Tucson AZ. Steve has worked extensively on Kitt Peak where he has had the roles of telescope scientist, Instrument scientist, and most recently project scientist for the Mosaic camera upgrade. Research areas include binary stars, exoplanets, and CCD instrumentation. Steve is currently working extensively with the NASA Kepler mission and its quest to find Earth-like planets.
Rob Sparks is a science education specialist in the EPO group at NOAO and works on the Galileoscope project (www.galileoscope.org), providing design, dissemination and professional development. He also blogs at halfastro.wordpress.com.
Today’s sponsor: This episode of 365 Days of Astronomy is sponsored anonymously and dedicated to the memory of Annie Cameron, at the time of NASA EPOXI flyby of Comet 103P/Hartley 0.0.155 AU above Tryphena, Great Barrier Island, New Zealand, located between Betelgeuse and Procyon on the edge of Canis Minor 4 November 2010.
Transcript:
Rob: Hi, and welcome to this episode of the 365 Days of Astronomy podcast. This is Rob Sparks. I work in the Education and Public Outreach Group at the National Optical Astronomy Observatory and I am here today with Steve Howell.
Steve: Hi, Rob, how are you?
Rob: Good, how about you Steve?
Steve: I’m doing fine today.
Rob: We’re here today to talk about the Mosaic imager, the new Mosaic Imager at Kitt Peak, but first I’d like you to tell me a little bit about yourself and your position here at NOAO.
Steve: Okay, well, I am what’s called a staff astronomer here so I spend some of my time doing research and I spend the rest of my time doing work for the observatory and for the last few years for the observatory I have been working on building instruments for Kitt Peak.
Rob: Okay, that’s great. So we are talking about the new Mosaic imager at Kitt Peak. I understand this is an upgrade to the original camera. Can you tell me about the original Mosaic imager?
Steve: Sure, the original imager was built maybe 12 years ago or so and it consists of an 8k by 8k array of CCDs. For those of you who don’t know what the 8k lingo means, it means 8,000. And there are eight CCDs in the old mosaic imager and each of them had pixels of 4000 on one side and 2000 on the other side. The new Mosaic imager has very similar CCDs. They’re manufactured by a different company and they’re far better in many properties which we can talk about. But the old Mosaic was a workhorse instrument. It imaged a patch of sky about the size of the full Moon. And for those of you that have small telescopes or even large telescopes like professionals with CCDs, that’s a pretty big piece of sky. Generally you look at something that’s, you know, you maybe see half a crater on the Moon or something like that at best. So it’s quite a footprint on the sky.
Rob: And this upgrade is part of a program called RESTAR I believe. What is RESTAR?
Steve: Absolutlely. RESTAR is an acronym which I probably can’t remember but its something to do with revitalizing small telescopes and in the new lingo of the day small telescopes are any telescopes which are four meters in aperture or smaller so for some of us I still think of four meters as a pretty big telescope.
Rob: Yeah, so do I.
Steve: So this is a program that has been around for about three years. An NSF funded project, and it’s a project that wasn’t just open to the National Observatory. It was open to people that had telescopes in that size range, say from one meter up to four meters, where they could propose and get some money to do something. Something could be making the telescope work better, getting a new mirror, building a new instrument, many kinds of things along those lines. But the trick was you had to provide some sort of access to your telescope for the general astronomical community. So if you were at a private observatory, obtained some money from RESTAR to, I don’t know, buy a new CCD camera, then you would have to provide some of your observing time to the public.
Rob: So you mentioned the CCDs are being upgraded. What other changes are being made to the camera in this upgrade?
Steve: There are changes also to the controllers. These are the electronics that read out the CCDs and take the electrons you’ve collected from whatever you’re looking at and send them off to the computers, and again the old ones were 15 year old technology the new ones are far better and far faster so for some of you that struggle with readout time you will appreciate this. The old readout time, it would take almost three minutes from the time your shutter closed to the time your image was available for you to look at. The new ones will take 22 seconds. So it’s quite a difference in speed. For the astronomer what that means is you can get a lot more time on sky and a lot less time sitting around waiting for CCDs to read out.
Rob: That cuts out a lot of the dead time.
Steve: Absolutely.
Rob: Okay, so how will these science upgrades expand the science capabilities of the instrument.
Steve: Well they will expand it in a number of ways. The quantum efficiency of the new CCDs, and that’s how well they collect, and that’s how well they collect photons from the sky, quantum efficiency is up about 15 or 20% in certain bandpasses. That means you can get to the same signal to noise or you can integrate shorter to acquire data. The readout time we just talked about, that’s a big plus. And also the CCDs have much better properties in terms of their noise characteristics than the old ones. So if you combine all three of those together into some sort of efficiency factor, how much better you can do in terms of science, it’s about an improvement of a thousand or two thousand or something like that.
Rob: Wow! That’s quite an upgrade isn’t it?
Steve: It is indeed.
Rob: So what filters are here? What sort of wavelengths does this instrument look at?
Steve: This instrument can observe from the atmospheric cutoff at about 350nanometers all the way up to a little past one micron. So it’s everywhere the CCDs are effective. Filters available for it: there’s a wide array of filters, probably something like 100 filters that are broadband things that many of you might know about like Johnson BVR system, the Sloan filters, and many narrowband filters for specific science purposes.
Rob: But I assume it doesn’t hold all 100 filters at one time.
Steve: No it doesn’t not at all. It can hold 12 filters at once.
Rob: That’s still a pretty good number. So I understand commissioning was scheduled to begin late last year in October or November, somewhere in there?
Steve: Indeed it was.
Rob: What’s the current status of commissioning? How’s that going?
Steve: We had three commissioning runs in late October/early November and in December. We also took two nights in January that were slated for engineering work and we kind of glommed onto them and used them for commissioning. Commissioning went almost flawlessly and its completely finished. The camera has been used for science since early December so the project is essentially done. There’s always improvements you can make. There’s always a laundry list of to dos and those are being worked through.
Rob: What types of science are enabled by this camera’s expanded capabilities.
Steve: It could do a number of things similar to what it did before but the new science that will be able to come out of this upgrade will be larger surveys because you can spend more time on sky and less time waiting for your camera to read out, your observing efficiency goes way up. So for example in one observing night you may have been able to take 30 images before now you will be able to take 300. And each of those can cover a different part of the sky so the amount of area you can cover goes way up. And because the CCDs have much lower read noise and other noise due to the CCDs themselves and the new controllers, you can observe much fainter objects by about a factor of three.
Rob: Are you aware of any big new projects being undertaken with this new camera?
Steve: You now its just starting to go. I don’t know of any yet but there have been a number of proposals submitted in what’s called the NOAO Survey Proposals and those are being reviewed and will be projects that give people maybe a hundred nights of time on the telescope over a three year period to carry out large surveys. I know myself am very much interested in using this camera on another telescope on Kitt Peak. This camera was built and mostly used at the Kitt Peak Four Meter, but it also can be used at the Kitt Peak 0.9 meter, almost a one meter telescope. And there it has a really big advantage of the fact that the telescope, being a smaller telescope, provides an even wider field of view. And the seeing, and for those of you out there who don’t understand seeing, seeing is sort of how much the atmosphere causes turbulence in your image quality. And astronomers would really like the seeing to be a good number, that is for the turbulence to be really low so your images are very sharp and clear. And so the seeing at the 0.9 meter is not quite as good as the seeing at the four meter. But if you are doing a project for photometric work and not so much for imaging work then you can take advantage of another feature these new CCDs have. That is you can read them out, you can read them out in a mode called binning, you add every four pixels together and then your readout time becomes eight seconds. So now you hardly have any dead time whatsoever and you can do enormous areas of the sky on any given night.
Rob: And that gives you a larger field of view of, what is it about a degree across or so?
Steve: It is, absolutely.
Rob: So you can really do some nice wide field work with that.
Steve: You bet, so I am looking forward to proposing for that and we’ll see if the allocation committee likes my proposal.
Rob: Anything else you would like to add about the Mosaic imager?
Steve: Well, I think it’s a great upgrade. It’s a great project and a wonderful way to breathe new life into old telescopes and old instruments by upgrading them to modern technology. I encourage you all either as people who use it or look for data for it on the NOAO archive pages or if you are here for a tour make sure to ask people about it and they’ll show it to you.
Rob: And I assume that there will be images posted shortly in the image archive from this new camera.
Steve: There will be. I believe there are already some there so go look for those. There’s one that’s just an amazing image of a nebula that looks very much like the Firefox logo for those of you that use Firefox as you web browser and so we sort of joked about getting Firefox to sponsor us if we show them this image.
Rob: I’ll see if I can find that and link to it in the show notes.
Steve: Okay, great.
Rob: Thanks for joining me today, Steve.
Steve: You bet. Thanks, Rob.
Rob: Thanks. This is Rob Sparks from the National Optical Astronomy Observatory. Thanks for listening to this episode of the 365 Days of Astronomy podcast.
The image of the nebula that resembles the Firefox logo is Sharpless 2-188 and can be found at http://www.noao.edu/image_gallery/html/im1065.html.
End of podcast:
365 Days of Astronomy
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