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Can I (amateur astronomer) detect extrasolar planets?

  1. Jun 14, 2009 #1
    So... Can I (amateur astronomer) detect extrasolar planets? I've seen some videos on how they are detected (by measuring radial velocity (I love this word:biggrin:) of that planet). But they said nothing about the instruments used in detecting these things. Can they be bought/made?
    I'm guessing it can be done, but with many, many $$$.
     
  2. jcsd
  3. Jun 14, 2009 #2

    russ_watters

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    Yes, it can be/has been done by amateurs. The primary method for amateurs is collecting brightness data over a period of time and measuring periodic dips in brightness from a "hot Jupiter" (large, close orbiting) type planet transiting in front of the star. The equipment you'd need can probably be had for $5000 USD or less. That's the order of magnitude cost of my setup and I'll probably give it a shot at sometime myself. IIRC, Sky and Telescope did an article a year or two ago, giving a couple of examples of planets already discovered via this method that amateurs could use to test their ability to duplicate the discovery. That's what I'd suggest and what I will probably do sometime.

    Googling, here's an example from 5 years ago: http://www.skyandtelescope.com/news/3309506.html

    That guy's equipment is closer to the $10,000 range, but I don't see why it is necessary to be quite that high end. All you are doing is detecting brightness variations, so you need only a telescope that can pick up and track the star well. The more important piece of equipment is the camera, (and his was expensive), but there are good quality cameras that I would think would work for this that can be had for $500-$1000.
     
    Last edited: Jun 14, 2009
  4. Jun 14, 2009 #3
    Well thats a lot of money in my book, for now at least. Who knows what the future holds, right?
     
  5. Jun 15, 2009 #4

    russ_watters

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    Hmm, well... not sure what kind of price range you had in mind. I can't imagine doing this without a self-tracking mount, for a start. The telescope is the biggest variable, I don't really know what you need for optics. Perhaps you can do it with something relatively inexpensive, but it needs to pull in enough light for a strong signal.

    Buying the equipment new, here are some cheaper possibilities:

    An Orion Skyview Pro 8, 8" equatorial, computerized reflector: $1200
    http://www.telescope.com/control/pr...ctors/~pcategory=telescopes/~product_id=24731

    Here's a low res but high quality ccd camera for $400: http://www.optcorp.com/product.aspx?pid=319-320-1214-1285-10632 [Broken]

    Now with such a setup, it'll be able to help you find the star and track it, but you'd need to check every few minutes to an hour (depending on how well it is aligned) to keep the star centered. The computerization isn't essential, but unless you are an expert, you'd have no hope of finding the right star manually. And tracking it manually for hours would almost certainly be out of the question.

    Here's a free(!) book about it: http://brucegary.net/book_EOA/x.htm

    Googling, most of the sources I've seen put the specs I listed at first at the minimum, but I'm not sure I buy that the standards must necessarily be so high. For my first effort, I certainly won't care about a contribution to science: I would only care about proving to myself I can do it.
     
    Last edited by a moderator: May 4, 2017
  6. Jun 15, 2009 #5

    ideasrule

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    Amateur computerized mounts are nowhere near accurate enough to place a faint, unremarkable star so close to the center of the field of view that the observer can unambiguously identify it. The best one can hope for is for a few bright stars surrounding the target star to come into view, so that these stars could be found on a star map and the star map could then be used to find the target.

    Regarding tracking: I agree that manual tracking is difficult. Automated tracking using computer software is much easier and more accurate, so in this regard a computerized mount is pretty much essential.
     
  7. Jun 15, 2009 #6

    russ_watters

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    Well, it depends on how crowded the sky is where you are looking. My mount has an advertised pointing accuracy of 1 arcmin, and there are many places in the sky where 9-12th mag stars are far enough apart for that. But yeah, it would be better to find one near an unambiguous, much brighter star.
    I was talking about passive tracking via the mount alone, but yes, computerized autoguiding would be much better.
     
  8. Jun 16, 2009 #7
    Soon I should get an 250mm F3.5 Reflector (optical tube only). So i just need good quality mount and a camera. That just might be in my price range :biggrin: . Thanks for the info.
     
  9. Jun 16, 2009 #8

    ideasrule

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    If you do try this, try measuring the brightness of a few variable stars to test the accuracy of your equipment. Many of these stars have well-known and highly regular light curves that you can search up online.
     
  10. Jun 16, 2009 #9

    ideasrule

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    Your mount's much better than mine; I've never been able to get my mount to be more accurate than 20 arcmin or so. But then maybe that's because I like observing on grass fields, and the ground sinks a little as the telescope moves since the scope is weighted on one side.
     
  11. Jun 16, 2009 #10

    russ_watters

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    I have an Orion Atlas, which retails for about $1500. IIRC, their next mount down, the Sirius, has similar pointing accuracy.

    My primary imaging setup has about a 16x12 arcmin field of view, so to reliably get an object in the field of view, I need better than a 6 arcmin pointing accuracy. In practice, I probably get 2-3, though I haven't really made an attempt to quantify it.

    I don't generally follow the proscribed alignment method anyway. Since I usually only image one or two objects a night, I do a one-star alingment on the nearest top 50 bright star to my target, then slew from there. Usually, that's less than 20 degrees away, so that helps with the pointing accuracy.
     
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