= Sirius intensity interferometry experiment
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In their 1956 <Sirius> report, <Robert Hanbury Brown> and <Richard Q. Twiss> used two 1.56-m searchlight reflectors feeding <photomultipliers>. The <photocurrent> fluctuations passed through 5–45-MHz amplifiers; an adjustable delay aligned arrival times. A linear mixer multiplied the outputs; an integrating motor accumulated their product. A second motor monitored its root-mean-square fluctuation to control gain changes. Separate lamps illuminated capped <photomultipliers> before and after observations to test electronic coupling and drift; blank-sky runs tested correlated <sky background>. They fitted a uniformly bright disk and an unknown zero-baseline scale to relative correlations at different <interferometric baselines>. Broadband response and possible baseline-dependent <systematic errors> limited the diameter inference.<A Test of a New Type of Stellar Interferometer on Sirius by Robert Hanbury Brown and Richard Quentin Twiss>[pp. 1046–1048: reflectors, delay/correlator, lamp and sky controls, relative-baseline disk fit]{ref}
This astronomical test extends the preceding laboratory <Hanbury Brown and Twiss effect> to two independently collected samples of a <star>. The historical motor reading was an instrument-specific correlation statistic. It should not be identified numerically with the normalized $g^{(2)}$ below without the corresponding <measurement calibration>.
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