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Why Not Always Observe at Maximum Resolution with a Radio Telescope Interferometer?

18 May 2014, 11:35 UTC
Why Not Always Observe at Maximum Resolution with a Radio Telescope Interferometer?
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Question: Best angular resolution is achieved with the NRAO dishes at their maximum separation. I do not understand why less than maximum separation is often used. Can you please give some examples of projects done at NRAO which actually benefited from less than best angular resolution.
I am an astronomer, although I work at visible light wavelengths with no familiarity with radio telescopes. But I should be able to understand the technical language of what you are observing far beyond the solar system.
Thank you for your service.
Sincerely yours,
Frederick Pilcher
Answer: As you correctly point out, radio telescope interferometers (or even optical interferometers) attain their highest spatial resolution when they are at their maximum separation. To understand how the separation of a telescope array elements relates to the spatial scales to which it is sensitive, consider first a single telescope. The maximum resolution attained by a single telescope is inversely proportional to the diameter of its light collecting surface (dish surface for a radio telescope, mirror for an optical telescope). You have an instrument that is sensitive to source sizes that are proportional to your spatial resolution, but nothing larger or smaller than that. If you then connect ...

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