Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Issues with the use of telescopesLong wavelength (Radio) AstronomyResolution RevisitedRadio telescopes have relatively poor ability to resolve objects because of the long wavelength of the EM waves.Issues with the use of telescopesResolutionFor the National Radio Astronomical Observatory Robert C. Byrd Radio Telescope, wavelength 1 m = 1 x 106 m Diameter of the aperture (the objective) = 100 mmin 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 diametersThis is the worlds largest fully steerable radio telescope min (in arc sec) = .25 (in m )D (in m)Issues with the use of telescopesLong wavelength (Radio) AstronomyInterferometrySolution: 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.Issues with the use of telescopesInterferometryDmin (in arc sec) = .25 (in m )D (in m)D Signal Combinedmin (in arc sec) = .25 (in m )D (in m)Issues with the use of telescopesInterferometryVery high resolutions can be obtained even if the wavelengths are very
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