Date: December 23, 2010
Title: Basic Spectroscopy for Amateurs, part 2
Podcaster: Mark DeVito and Tom Field
Description: A brief discussion of basic spectroscopy. Part 1 of this podcast aired on Dec. 8, 2010.
Bio: Mark is an amateur astronomer in Fredericksburg, Virginia and just getting into amateur spectroscopy. Tom Field is an amateur astronomer and amateur spectroscopist from Seattle Washington.
R-Spec Software: www.rspec-astro.com
Amateur Spectroscopy: http://www.amateurspectroscopy.com/
V-Spec Software: http://astrosurf.com/vdesnoux/
Christian Buil: http://www.astrosurf.org/buil/
Robin Leadbeater: http://www.threehillsobservatory.co.uk/astro/astro.htm
David Haworth’s Spectroscopy Links: http://www.stargazing.net/david/Spectroscopy/links.html
Shelyak Instruments: http://www.shelyak.com/?lang=2
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Wayne Robertson, who encourages you to join him in supporting this great podcast.
Additional sponsorship for this episode of “365 Days of Astronomy” has been provided by Mike Smithwick, author of the award winning astronomy software, Distant Suns, now for the iPad and iPhone.
Mark: Hi, and welcome to Part Two of the 365 Days of Astronomy Amateur Spectroscopy podcast. My name’s Mark and I’m an amateur astronomer and soon to be amateur spectroscopist in Fredericksburg, Virginia and today I’m going to be joined by my co-host, Tom Field, an amateur astronomer and amateur spectroscopist in Seattle, Washington. Hi, Tom. Welcome to the show!
Tom: Thank you very much, Mark.
Mark: So, Tom, before we get started with talking more about spectroscopy specifically, why don’t you tell us a little bit about your experience with astronomy and what brought you to the point where you are.
Tom: Sure! I’ve been in astronomy, doing it for fifteen or twenty years. I’d done a fair amount of visual observing, a little bit of imaging. I was finding that I didn’t have the excitement that I had early-on in the hobby. It was very exciting early-on to take images and to learn a lot about what I was observing. But that wasn’t sustaining me anymore. I found that I needed something more exciting to do.
And that’s where as I was looking around I saw the field of spectroscopy as a field that was accessible, one in which I could, as an amateur, still do scientific-type observations. So it’s been a lot of fun to get into it and it has rekindled that excitement that I’ve got for astronomy.
Mark: How long have you been doing spectroscopy?
Tom: Spectroscopy, I think it’s been two or three years now I’ve been doing it. I’ve been wanting to do it for a long time and I think there’s probably a lot of people out there like me who wanted to get into it but just weren’t sure how to get into it. Or, they tried and they couldn’t find the tools they needed to figure out what they needed to do.
Mark: Earlier on, in the previous broadcast of the first portion of the podcast, I mentioned that it is sort of a niche within a niche. And, I think that was your description when we’ve spoken about this in the past. I think that really is a good way to describe it.
Tom: Yes, it is a niche in a niche. You’re right. But the nice thing is that there are so many amateurs today that have the equipment they need and have the interest and the skills. So even though it’s a niche, it’s mostly a niche in terms of the number of people who are doing it, but not the number of people who might be interested in doing it.
Mark: Gotcha. So you mentioned that most people have the vast majority of the equipment that they need to need to do that. What type of equipment would an amateur need to start exploring this area?
Tom: Getting started is really easy because most amateurs have most of the equipment they need. A standard telescope – not even a big aperture – to do amateur spectroscopy is needed. And most amateurs have a classically -cooled CCD camera or a video cam like an Imaging Source video cam. That’s really the core of the equipment platform that’s needed to do this kind of observing.
Of course then they need to add a small diffraction grating which comes in a filter cell. And they sell for about $120 typically. It screws into the telescope. So it’s easy to get in and get some preliminary results and to see what the excitement is about and if it’s their cup of tea. For some people, they may try it and say, “This isn’t for me.” But my experience has been that when people see the kind of data they can get, they’re really getting hooked very easily these days.
Mark: Now you said that the diffraction gratings are right around $120 or so. Who are the manufacturers that a beginner would look at to find something like that.
Tom: Good question. Incidentally, there are two primary vendors of low-cost, low resolution diffraction gratings. The first is grating called the “Star Analyser.” And that’s out of Europe. It’s the one that’s most recommended because it’s designed for the kind of imaging we’re going to be doing with CCD cameras .
There’s also one here in the US from Rainbow optics. It has a little higher resolution. It doesn’t work out quite as well, I’m told, with a variety of CCDs. But there are people using them and getting good results with them also.
Mark: Now I think the Star Analyser, the manufacturer is Paton Hawksley if I remember correctly.
Tom: That’s correct. And that can be bought directly from the manufacturer, or from a variety of vendors on the web.
Mark: Ok, great. Now, if you don’t have telescope or CCD? I know a lot of people have moved from using a traditional cooled CCD like an SBIG camera or something like that to either webcams or even connecting their DSLR. Would those be acceptable as well for [spectroscopic] imaging?
Tom: Yes. The webcam is a really good approach for someone getting started because it gives immediate feedback of the observations you’re getting right in the field. So there’s no a lot of complicated data reduction that has to be done downstream. And, remarkably, the new Canon and other DSLR cameras do very well. And the diffraction grating literally can just be mounted right on the front of the lens on the camera for good results to be gotten. It’s pretty remarkable.
Mark: Excellent! So these diffraction gratings can also be screwed into the eyepiece, you can also do visual spectrums as well. You don’t necessarily have to image it. Although that’s obviously where your data collection would come from. But you can even do it, as an example, if you’re an amateur who does star parties, you can put that on your eyepiece and show the public what the spectral pattern is for whatever object you’re looking at.
Now once you have your equipment set up, and you’re able to get an image of your object and your spectra, where does an amateur go from there? Where do they do a data reduction? Where do they start getting science out of the imaging and of the spectra?
Tom: One thing that’s interesting about spectroscopy is that there’s very little initial image processing done. Of course, amateurs that are doing visual imaging spend a lot doing a lot of adjustments, for example un-sharp masking, to create an image that is aesthetically pleasing. But when you’re collecting data for science, there’s not a lot of pre-processing to be done because you don’t want to taint that data or move it away from what the photons were that came in through the telescope.
The processing can typically involve stacking the images which is something most amateurs are already familiar with. Maybe some dark frames. But other than that, the processing of the images is pretty easy. It’s really just converting that smudge (that’s like a rainbow but typically it’s going to be black and white) into the characteristic graph that we see in the magazines. And those graphs will have of course a dip in various places that are the result of various elements that are surrounding a star or planet.
Converting an image to those graphs done in software. There’s some freeware out there that comes from Europe and is partially translated into English. Also, I’ve written a program called RSpec which will do the same thing. I’m a little biased: I think it does it a little more easily. And the neat thing about it is that it will do it real-time off a video or still image. So you capture an image and through the software you can actually plot the graph. So you can see exactly what you’re observing while you’re observing it. It’s very exciting!
Mark: Excellent. Now what kind of computer do you need? Can you do this on a standard computer? Is it Windows, Mac?
Tom: Good question. Yes, it’s all Windows-based. And for some of the real-time operations, you need a little bit more horsepower than a five or ten year old laptop. But it’s remarkable what hardware that’s three or four years old can do now. It can strip the images of information, stack the data automatically, show the graph and actually synthesize a color profile so you can see what you’re actually capturing.
Mark: So after you’ve captured your data? Now we’ve gone from the amateur collecting his image, collecting the spectra, he now has his software that he processes it through. What kind of data can you capture? What projects can be done? What can you learn and understand for it?
Tom: The first night out typically a amateur is going to image is a bright star like Vega. What they’re going to get is one of these profile graphs that will have dips in it for various Hydrogen absorption lines. Getting that graph and then calibrating is the next step. Typically it’s done after the fact. And, calibration can be somewhat of a challenge. You have a graph and you have to calibrate it in Angstroms as opposed to pixels that are coming from your camera. But, there’s a lot of information out there on the web. There are books that help figure out what your calibrations are. And, surprisingly , there’s very active amateur community on-line that will be of great assistance to anybody who’s getting into this field in answering these kinds of questions.
Mark: The amateur groups can be found under “spectroscopy” in the groups on Yahoo. Is that correct?
Tom: That’s correct. Mark, I wanted to mention some of the other kinds of things that people can do once they’ve gotten a little more comfortable with the observing process and capturing data for spectroscopy. It’s very easy in a backyard setting (even in the city) to get really interesting results. One of the great things about spectroscopy is that it’s not nearly as dependent on dark skies as visual imaging. This is because in spectroscopy, by definition, we’ve actually spread the spectrum out. So we can ignore the parts of the spectrum where there’s urban light pollution.
So, some of the remarkable results that are coming out of the European amateur community are being done right in their cities. In fact, Europeans are typically leading the amateur community in developing this kind of technology.
The kinds of things you can do in a backyard with an 8” scope and a very simple camera include capturing images of Neptune’s spectrum and detecting the methane absorption bands. Or seeing the emission lines on M42, the Orion Nebula. In fact, Robin Leadbeater is the designer of the Star Analyser and has done a lot of path-breaking in this field. In his backyard, using a 9” telescope and just a modified webcam, was able to image the quasar QSO 3C 273 and easily detect the red shift [from the expansion of the universe.] So this is the kind of data that almost anybody can get. They don’t need to have a mega-telescope or a dark sky site.
Mark: I’m just at the beginning level of spectroscopy myself, Tom, but it sounds to me that because there’s a minimal amount of equipment necessary, and you can do it in light polluted environments, that spectroscopy lends itself well also to school projects for high school students or for scouts or astronomy clubs or star parties to expose people to an entirely and somewhat unique area of amateur astronomy. That’s very cool.
Tom: Well, that’s true, Mark. I don’t know how many of our listeners stumbled into a star party somewhere and some very excited amateur showed them M42. My experience was that I looked through the eyepiece and thought, “That’s just a smudge! Why would I be interested in that?” It took some time to get some background so I could get excited about these kinds of things. One of the things about spectroscopy, especially real-time spectroscopy, is you get color. And color adds sizzle. You can show them the rainbow. You can show the gaps in the spectral rainbow displayed right on your screen.
I’m seeing more and more high school students come to various websites saying that they’d like to do spectroscopy. Frequently a parent will say, “My child or teenager is trying to do a spectroscopy project. Is this a good direction to go?” And it definitely is a good direction to go because you can get results without having a lot of expensive apparatus or experience.
I wanted to mention that as somebody grows in experience they can of course throw money at this just like any equipment. The pioneering work that’s being done by the European community now is really remarkable. They’ve developed a high resolution amateur spectrograph (LHires III) that sells for about $3,000. And they’re really doing remarkably good observing.
There are some actual “pro-am” professional-amateur collaborations where the amateur community in Europe as well as in the US are collecting data on certain particular objects, “Be” stars in this case. Amateurs are contributing data to the scientific community and actually participating in publication. So it’s not just that this is something an amateur does on his own and gets low-resolution results. You can grow pretty easily into doing things that are actually scientifically significant and contributing to our advancement of understanding.
Mark: You know, the internet really is your friend. We mentioned the spectroscopy groups on Yahoo. We’ll have some of the links to websites listed in the 365DaysofAstronomy website. Tom, would you like to provide the URL for your site.
Tom: Sure. The name of the software that I’ve written is “RSpec. That stands for rapid or “Realtime Spectroscopy.” It’s www.rspec-astro.com.
Mark: So, thanks a lot everybody. We appreciate it and, Tom, thank you for your time.
Tom: My pleasure.
End of podcast:
365 Days of Astronomy
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