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tom--rspec

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About tom--rspec

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    http://www.rspec-astro.com
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    tomfield1952

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    Seattle, Washington, USA
  1. Yes, Bill, as Merlin points out, you'd want to do a quick instrument calibration. Check out video 15 on the RSpec site: http://www.rspec-astro.com/more-videos to see how it's done. Tom
  2. An easier (IMO) way to determine your DSLR's spectral response is to take a spectrum of a bright type A star like Vega. You don't even need tracking. See the details at this link. It's rather remarkable what a DSLR can do spectroscopically. See, for example, what Janet SImpson did with a 30 -second exposure on her DSLR with simple mechanical tracking: link. Tom
  3. Th RO grating is 200 lines/mm. The SA is 100 lines/mm. So, the RO grating will spread the spectrum out twice as much as the SA. The images you posted already had so much dispersion that the star wasn't visible. (The calibration in my video showed dispersion of about 3 Angstroms/pixel in the label just above the graph. That much dispersion also makes imaging dim objects more difficult because the light is more spread out.) Doubling the dispersion is the opposite direction of what you need! If you're mounting the grating on the front of a DSLR, just reduce your lens' focal length (zoom). If you're using the grating between your camera and your telescope, the you'll need to decrease the distance between the sensor and the grating. If you want to explore a bit of the math around grating spacing, check out this write-up: link. There's a link there to a simple Excel workbook (SimpleCalc.xls) that lets you estimate where the grating should be placed. The good news regarding grating spacing is that, unlike focusing for example, it's not critical to get it "exact." There, in fact, is no perfect grating spacing. Just get it approximately right, and then get out and then have fun doing science! Also, for an example of how background subtraction is done, check out video #10 here: link.
  4. Hi, Jack! Nice spectra. I made a quick YouTube video that shows how it can be calibrated: Calibrating a Star Spectrum - YouTube On Youtube, select the buttons at the bottom of the playback so that it plays it in HD, full screen so you can see what's going on! As I mention briefly in the video, calibration of unknown spectra is much easier if you can see the star (called the "zero-order" along with the spectrum. Move your grating a bit further from your sensor to lower the dispersion. (Or, unzoom your DSLR if you're using an objective grating on the front of the lens.)
  5. Hi, Chris, If you need more time on the trial period of RSpec, please drop me a line via RSpec site's contact form. I'd be happy to extend the trial period as you need. Congratulations on your entry into an exciting branch of amateur astronomy! Tom Field RSpec / Real-time Spectroscopy
  6. I thought some of you might like to see this ten-minute video interview in which I discuss how easy it is to get started in spectroscopy. I also demonstrate my real-time software in action. The video was made by Sky & Telescope Magazine at last month's NEAF conference. Link to video.
  7. Hi, I'm the author of RSpec, the new real-time spectroscopy program mentioned earlier in this thread. As you might guess, I've given a fair amount of thought as to why spectroscopy hasn't caught on more than it has in the past five or ten years. Please forgive me for the lengthy posting below. Here's my story: Several years ago, I bought a Star Analyser grating, expecting to have some fun. I didn't have fun. Even just capturing images was difficult because I couldn't even see if I was doing it right until the next morning when I post-processed the data. And, the next morning? Total nightmare. I had to jump through four unrelated programs to convert my data (with no documentation explaining the process). The final program that I used to process the spectra, although justifiably very popular, wouldn't install, then installed but kept crashing erratically. Its manual was mostly translated into English, but seemed to be aimed at people who already knew spectroscopy. I believe the biggest obstacle to wide-spread adoption of spectroscopy by amateur astronomers is that, up until now, the only software that has been available has been difficult to learn and use. (It’s also astonishingly powerful -- more so than RSpec will probably ever be.) Where I believe my software can make a difference is that because of its ease of use, it opens the door to newcomers. With RSpec and an inexpensive grating, you can learn the field and get fascinating results. It was the frustration I experienced in my first attempts at spectroscopy that I led me to write RSpec. I wrote it for a selfish reason: I wanted a tool for myself that allowed me to do spectroscopy easily. The on-line spectroscopy community has been wonderfully supportive of my work. High caliber experts with skills and experience like Merlin66 have been very helpful in providing me feedback and suggestions. And the resulting software hopefully reflects that. I've been writing software professionally for more than 25 years. I put everything I've learned over those years into the program: software engineering, user interface design, work-flow, multi-threading, tiered-complexity, software testing and QA, and, most importantly: user education -- i.e. how a new user learns. RSpec comes with twenty on-screen video tutorials (a total of about 60 minutes' worth). They walk a new user step-by-step through the process of capturing and processing a spectrum. If you have a camera of any sort, with RSpec and a properly mounted SA grating you can capture a live spectrum on your first night out... guaranteed! It's quite exciting! I'm proud of RSpec's user community. I think it demonstrates that with the right software and educational materials, anyone can learn spectroscopy if they’re interested. For example, there's a 75 year-old man in Oregon, who had never done spectroscopy until two months ago. He is now at the intermediate level and asking all the right questions! And he's so darned excited about what he's learned that his enthusiasm is contagious. The amateur spectroscopy community has been well-led by the path-breaking work of the European community. For instance: Robin Leadbeater developed the Star Analyser and published some remarkable results on his website. The French developed a wide range of tools and techniques: from software to hardware, including the wonderful $3,000 LHiRes III spectroscope. (They're now doing research-quality observing, contributing to professional efforts.) Our Merlin66 here has created an intermediate resolution spectrometer. And he has has written a book that we're all looking forward to owning in a few weeks. :-) The other major obstacle to more amateurs getting involved in spectroscopy is the myth that it requires dark skies, large aperture, near-professional skills and a PhD in physics! That all might have been true at one time, but, these days, there are tools and community that make it relatively easy, as the 75-year old mentioned above discovered. No, spectroscopy isn't for everyone, as noted earlier in this thread. Some amateurs aren't interested in graphs and data, preferring the aesthetic beauty and accessibility of visual imaging. However, there remain a large number of amateurs who would like to collect objective data with their gear, but are intimidated by spectroscopy because of the perceived difficulty. I think that the time is ripe for them to get involved in spectroscopy. But don't take my clearly-biased word for it. The RSpec site has lots of videos, examples of sample projects, and a free, fully-enabled trial version of the software. If you're being held back by your wallet, or lack of equipment, knowledge or weather, then the site has a sample .avi video file that you can download so you can immediately start experimenting with spectroscopy. I invite you to try it out. And then post back here or email me with your results! Personally, I've found that getting involved in spectroscopy has enormously deepened my understanding and engagement in astronomy. Once you're doing spectroscopy, you tend to read the available literature (Astronomy Now, Sky & Telescope, etc.) with a much better eye. Things that you formerly skimmed you're now reading and actually understanding! There's nothing more exciting than new knowledge. Thanks for the opportunity to share my opinion. Of course I welcome any feedback. Tom Field www.rspec-astro.com
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