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Issues with the use of telescopes Long wavelength (Radio) Astronomy Resolution Revisited

Issues with the use of telescopes Long wavelength (Radio) Astronomy Resolution Revisited. Radio telescopes have relatively poor ability to resolve objects because of the long wavelength of the EM waves. Issues with the use of telescopes Resolution. λ (in μ m ). Θ min (in arc sec) = .25.

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Issues with the use of telescopes Long wavelength (Radio) Astronomy Resolution Revisited

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  1. Issues with the use of telescopes Long wavelength (Radio) Astronomy Resolution Revisited Radio telescopes have relatively poor ability to resolve objects because of the long wavelength of the EM waves.

  2. Issues with the use of telescopes Resolution λ(inμm ) Θmin(in arc sec) = .25 D (in m) For the National Radio Astronomical Observatory Robert C. Byrd Radio Telescope, wavelength ≈ 1 m = 1 x 106μm Diameter of the aperture (the objective) = 100 m Θmin≈ 2500” = 41’ = .69o The angular diameter of the moon = 30’ The angular diameter of the Andromeda Galaxy ≈ 178’ The NRAO telescope would be able (roughly) to resolve radio sources of these angular diameters This is the worlds largest fully steerable radio telescope

  3. Issues with the use of telescopes Long wavelength (Radio) Astronomy Interferometry Solution: Use multiple radio telescopes separated by a large distance. The separation between the telescopes is called the baseline. Signals are then collected from the two sources and then combined. In effect, the separated telescopes increase the effective diameter of the objective. The process of combining the signals from two (or more) receivers is called interferometry.

  4. Issues with the use of telescopes Interferometry λ(inμm ) Θmin(in arc sec) = .25 D D (in m) λ(inμm ) Θmin(in arc sec) = .25 D Signal Combined D (in m)

  5. Issues with the use of telescopes Interferometry Very high resolutions can be obtained even if the wavelengths are very long.

  6. VLA

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