THE STELLAR INTERFEROMETER AT NARRABRI.
SYDNEY UNIV (AUSTRALIA)
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The interferometer at Narrabri makes use of an intensity interferometer to achieve a max resolution of approx 0.0005 sec of arc. It is designed to measure the apparent angular diam of all stars brighter than magnitude 2.5 and with spectral type earlier than F. O. The instrument consists of 2 large mirrors 22 ft in diam which move on a circular track 618 ft in diam. The mirrors are controlled by a computer to follow the chosen star in azimuth and elevation. At the focus of the 2 mirrors there are photomultipliers which view the star through narrow-band interference filters. The output currents of the 2 photomultipliers are carried by coaxial cables to an electronic correlator which amplifies the fluctuations in the 2 currents in the frequency range 10-120 mcps and multiplies them together to measure their correlation. In operation the correlation is measured as a function of the separation between the 2 mirrors. A single observation at 1 spacing requires approx 3 hr for a star of magnitude 1.0. Author