How do astronomers measure the diameter of a star?

Since stars are too remote for any telescope to measure their diameters directly, how do astronomers know that Sirius is 1.8 times the diameter of our Sun or that Aldebaran is 45 times wider? The answer is indirect measuring techniques, which have yielded the diameters of several hundred stars.
The first method involves the precise electronic monitoring of a star when it is blocked out by the Moon. As the Moon makes its monthly orbital trek around Earth, it passes in front of many stars, but only occasionally are the stars bright enough for the detection equipment to complete the experiment. Although the technique is little more complicated than observing the length of time it takes for the star to disappear (which is almost instantaneous), it has revealed accurate diameters for several dozen stars.
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