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Plateau de Bure interferometer

Three telescopes of the Plateau de Bure Interferometer operated by IRAM. Each has a diameter of 15 meters. In the meantime, the array consists of six antennae.

The following photo suggests very clearly the high surface accuracy (and the size) of the antennae. One can see the neighbouring antenna's upside-down image in the top half of the dish. The surface has a mean error from the perfect paraboloid of about 60 micrometers. It is also visible that the telescopes are moveable on a railtrack.

Like all other millimetre observatories, the Plateau de Bure interferometer specialises in studies of line emission from molecular gas and radio continuum of cold dust.

At an observing wavelength of 3 mm (100 GHz frequency) each of these telescopes can resolve two objects 45" apart from each other on the sky. In an interferometer, these 45" are actually the size of the field of view. So an interferometer like this one images, at very high resolution (better than 1") structures smaller than 45". What does this tell us? Although for collecting a lot of radiation as quickly as possible it is desirable to have large telescopes, in the case of interferometers this can also be a disadvantage, because their field of view will be small. For observing more extended objects on the sky, one would want to have smaller individual telescopes providing a larger field of view, but many more so as to have the same telescope surface area as fewer large dishes.