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I read that radio telescopes have “huge fields of view (FoV)”, but are unable to precisely localized objects due to their “small instantaneous field of view (IFoV)”. Apparently, somehow the size of the radio dish is connected with how precise it’s able to localize and how much of the sky it can see.

How are field of view, instantaneous field of view, and the size of a radio telescope dish connected? What’s the difference between FoV and IFoV?

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  • $\begingroup$ You can point the dish over a large range, but it only sees a small bit of that at a time. The same holds for phased arrays (like the VLA). $\endgroup$
    – Jon Custer
    Jun 25, 2020 at 19:42

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for a given frequency, the diameter of the radio telescope determines the weakest signal it can detect. bigger dishes can detect weaker signals.

a huge field of view means the dish is focused out so that it is "looking" at a large sweep of the sky at a time, but in so doing it can't see very faint objects nor can it precisely measure the positions of all the objects it can see. Such a telescope is useful for doing low-resolution surveys of the sky.

Whether a given dish is suited for sky surveys or for closer looks at individual objects of interest depends on the details of its construction and whether or not it is connected up to other dishes so as to enable interferometry, which is how all the super-high resolution radio mapping of the sky is done.

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