Detwinkler

Everybody knows that stars twinkle, but no one is sure what makes them do it. Some scientists say that small irregularities in the air act like tiny lenses and make the stars seem to vibrate to & fro. Others think the twinkling is in the eye. Because the pinpoint star-images can cover only a few of the light-sensitive receptors in the eye's retina at a time, the slightest movement makes the star seem to jump and twinkle as the image moves from one group of receptors to another.

Astronomers, who do most of their observing with photography, have no answer to the controversy. But they are sure that twinkling of a sort goes on even inside their telescopes. The result is a fuzzy disc on the photographic plate which often ruins their work.

Last week graduate students in the electrical engineering department at Britain's Birmingham University were putting finishing touches on a "detwinkler" to make the stars hold still. The detwinkler uses photoelectric cells to keep watch on the star image. When the image starts to wander, they signal a pair of electric motors which move the photographic plate back in line. As far as the plate is concerned, that star doesn't twinkle any more.

In laboratory tests the detwinkler has worked well. Soon it will be tried on real stars with a big telescope. But even the detwinkler cannot make more than one star hold still. The rest of the stars in the field will go right on twinkling as cheerily as ever.

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