April 3, 1984

Through the slot in the observatory dome the astronomers saw the first star appear in the southern twilight. The sun had set. Earth had cast its shadow briefly out beyond the eastern horizon, creating a faint pink rim in counterpoint to the sun's more dazzling farewell. And now, clear as could be, there was the dog star Sirius, herald of night. Time for astronomers to go to work. Time to rehearse the coming of the astronomical spectacle of a lifetime, the 1985-86 appearance of Halley's comet. After sundown every day last week astronomers around the world, professionals and amateurs, peered into the southwestern sky for a glimpse of a fuzzy patch of light coming from 74 million miles away. This was the Comet Crommelin, small and faint, no Halley by any measure, but a suitable object for practice observations. It was passing earth at about the same distance and same position, some 25 degrees above the horizon, as will Halley in March 1986.

A three- judge panel today named Jacob A. Stein to conduct a broad investigation of charges against Edwin Meese 3d, the counselor to President Reagan and Mr. Reagan's nominee for Attorney General. ''We tried to find a competent man, a man who knows his way around the courtroom, an honest man,'' said Judge Roger Robb, who headed the panel of three senior judges from the United States Circuit Courts of Appeals. Last week the panel received an application for an independent counsel from Attorney General William French Smith. Mr. Stein, 59 years old, is an adjunct professor at the George Washington University School of Law, past president of the District of Columbia Bar and a fellow of the American College of Trial Lawyers. His trial practice with the firm of Stein, Mitchell & Mezines here has included both civil and criminal work. He was a defense lawyer in the Watergate investigations.

The Soviet Union, as part of an apparent reorientation of its trade among the leading industrial nations, strengthened its commercial ties with Western Europe last year. While trade with Western Europe grew by 6.4 percent in 1983, Soviet exchanges with other industrial countries, notably Japan and the United States, declined by 16 percent. This global shift in trading patterns is due in part to continued large Soviet sales of oil and natural gas, growing purchases of modern industrial technology and a decline in imports of grain. Buyers and Suppliers An analysis of trade figures released by Moscow shows that Soviet trade with the industrial democracies last year became increasingly focused on West Germany, Italy and France, the principal Western buyers of Soviet oil and natural gas as well as the largest Western suppliers of industrial machinery and equipment to the Russians.

Increasing evidence of widespread cheating and fraud involving the basic examinations that doctors must pass before they are allowed to practice medicine is being reported by medical educators, state and Federal officials and professional groups. In the last several years, all or parts of three of the four key tests involved in the process leading to the licensing of physicians have been stolen, reproduced and sold for prices as high as $50,000 a copy, the officials say. Nearly 100,000 students and doctors take the tests each year, and while officials say they cannot give an exact estimate of the number who cheat and they assume that the vast majority of those taking the tests are honest, they say cheating has become a significant and growing problem. ''The fraud relating to the tests is shocking,'' said Janet Carson, general counsel of the National Board of Medical Examiners, the professional organization in Philadelphia that drafts most of the tests. ''It's illegal and immoral and undermines everyone's faith in the medical profession.''

Spending for new construction, driven by continuing strength in the housing industry, soared by 6.9 percent in February, the largest monthly increase in almost four decades, the Commerce Department reported today. Officials said spending was at an annual rate of $295 billion, compared with $276 billion in January. The new rate reflected broad improvement throughout the construction industry, with particularly strong showings in residential and industrial building.