Eclipses to Order

Like a great dahlia, the sun is ringed with petals of light. The inner corona, one-millionth as bright as the sun's heart, is dazzling yellow, the outer corona pearly white, with delicate, wraithlike streamers. Often the corona is racked by violent eruptions that produce magnetic storms through the earth's atmosphere. But it is impossible to detect such phenomena with an ordinary telescope, for the sun's brilliance obscures its crown. For years astronomers rushed to the ends of the earth, chasing eclipses so they could photograph the corona for a few minutes while the sun itself was blacked out. Several years ago Bernard Lyot, an obscure astronomer of the Paris Observatory, invented the coronagraph, a combination telescope and camera that created an artificial eclipse.

Last week, Astrophysicist Donald Howard Menzel of Harvard announced construction plans for the world's highest astronomical station to house the first U. S. coronagraph. Site of the new observatory is Climax, Colo., a hamlet of 1,500 souls, perched 11,300 feet high on a pass of the Great Divide. Chief advantage of Climax is a daily cloudburst, which lasts about an hour, washes the sky an intense blue, clear as any in the Western Hemisphere. No drifting motes of dust can settle on the coronagraph lens to mar the view.

The principle of the coronagraph (which resembles an anti-aircraft gun--see cut) is simple. A metal disc is placed at the focus of the telescope lens to cut out the bright sun image. A second lens focuses on photographic film the black disc and flaring corona, and a powerful spectrograph breaks up coronal radiation into its component colors. A moving picture camera can also be attached to the telescope.

Coronagraph recordings may have great practical value. The magnetic storm which disrupted communications Easter Sunday was probably started, thinks Professor Menzel, when the earth coursed through the tail end of a corona streamer. Coronagraph experiments may help predict such storms in advance.

Also, said Dr. Menzel, "Coronal observations may furnish an index that statisticians can use, or perhaps misuse, in attempts to correlate solar activity with terrestrial affairs, such as the amount of ozone in the atmosphere, occurrence of aurorae, biological effects of radiation, meteorological phenomena, and perhaps some day, long-range weather forecasting."

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