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SESK: Stuff Everyone Should Know · sesk.info/astro-interferometer-separation

At a fixed wavelength, what sets how fine a detail an interferometer can resolve?

How far apart the telescopes are, not each dish's size.

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  1. The diameter of each telescope
  2. The distance between the telescopes ✔
  3. The total collecting area

Why: Two dishes 1 km apart resolve detail like a single 1 km dish. They do not collect that much light, though, because their real collecting area is still just the two small dishes.

Huh, didn't know that: The name sounds odd: the telescopes cooperate, and interference is the way their waves combine.

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Interferometers prove that sometimes the best relationships are long distance.
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References

Answer: The distance between the telescopes. Two dishes 1 km apart resolve detail like a single 1 km dish. They do not collect that much light, though, because their real collecting area is still just the two small dishes.

  1. OpenStax Astronomy 2e, 6.4 Radio Telescopes openstax.org/books/astronomy-2e/pages/6-4-radio-telescopes
    The resolution of an interferometer depends upon the separation of the telescopes, not upon their individual apertures.
    Checked 2026-10-10.

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