I saw this video at Space.com and I noticed that at 00:05 the animation illustrates waves propagating from space into The Dish at Parks Observatory, but at 00:50 the direction of propagation is reversed! Would there be some reason for transmitting - for example to create an artificial "star" for wavefront correction analogous to adaptive optics at visible wavelengths, or could it be simply a mistake in the animation?

Here are some GIFs from screenshots. You can check the video at the indicated times.

circa 00:05

at 00:05

circa 00:50

enter image description here

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    $\begingroup$ Its just a slightly dodgy graphic. No astronomical meaning. $\endgroup$
    – James K
    Feb 26, 2016 at 19:14
  • $\begingroup$ If you are sure @JamesKilfiger , can you add some supporting information and post it as an answer so I can accept it? $\endgroup$
    – uhoh
    Feb 28, 2016 at 9:47
  • $\begingroup$ There's a lesson to be learned here: Youtube (along with other websites that dish out videos, pun intended) is not the place to learn science. $\endgroup$ Feb 29, 2016 at 8:53
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    $\begingroup$ Maybe the lesson is really "consider the source." YouTube is just a library - you can browse the "tabloids", or go to the "bookshelves" for the good stuff. Plenty of top notch stuff available there. Note @DavidHammen - the source for the link in this question is a private, advertisement-laden site. $\endgroup$
    – uhoh
    Feb 29, 2016 at 11:55
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    $\begingroup$ screen shot of what I mean by "advertisement-laden" $\endgroup$
    – uhoh
    Mar 1, 2016 at 2:14

1 Answer 1


I guess it's a mistake in the animation. At radio wavelengths turbulence doesn't affect the measurments anymore and above 200 MHz the ionosphere doesn't play a role yet, so I guess the notion of a guide star is unnecessary here.

  • $\begingroup$ Thanks! That was a "for example" only: "Would there be some reason for transmitting - for example to create...". I'd like to find out for sure if there is some transmission of some kind, or if the video is wrong. $\endgroup$
    – uhoh
    Feb 26, 2016 at 18:05
  • $\begingroup$ @uhoh: Yeah sorry, I cannot tell about any other transmissions for sure, as I'm not a radio astronomer. $\endgroup$ Feb 26, 2016 at 19:18
  • $\begingroup$ Now you've got me thinking! Thanks! $\endgroup$
    – uhoh
    Feb 28, 2016 at 13:15

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