Editing Angular resolution (section)

===Telescope array===
The highest angular resolutions for telescopes can be achieved by arrays of telescopes called [[astronomical interferometer]]s: These instruments can achieve angular resolutions of 0.001&nbsp;arcsecond at optical wavelengths, and much higher resolutions at x-ray wavelengths. In order to perform [[aperture synthesis|aperture synthesis imaging]], a large number of telescopes are required laid out in a 2-dimensional arrangement with a dimensional precision better than a fraction (0.25x) of the required image resolution.

The angular resolution ''R'' of an interferometer array can usually be approximated by
:<math>R=\frac {\lambda}{B} </math>
where ''λ'' is the [[wavelength]] of the observed radiation, and ''B'' is the length of the maximum physical separation of the telescopes in the array, called the [[baseline (interferometry)|baseline]]. The resulting ''R'' is in [[radian]]s. Sources larger than the angular resolution are called extended sources or diffuse sources, and smaller sources are called point sources.

For example, in order to form an image in yellow light with a wavelength of 580&nbsp;nm, for a resolution of 1&nbsp;milli-arcsecond, we need telescopes laid out in an array that is 120&nbsp;m&nbsp;×&nbsp;120&nbsp;m with a dimensional precision better than 145&nbsp;nm.