What was going on when I was born?

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.

An independent auditor for the Public Service Company of New Hampshire, the lead builder of the Seabrook nuclear power plant, said yesterday that unless the company found additional sources of credit in the next three weeks, it might be forced into bankruptcy and find itself ''unable to continue in existence.'' The report came only three days after the 16 utilities that own the Seabrook project voted to cancel the plant's second reactor, if the partners could find a way to help Public Service of New Hampshire recover its $293 million investment. Last Wednesday, the utility said its banks, led by the First National Bank of Boston and the Morgan Guaranty Trust Company, had demanded that it find back-up sources of credit for Unit 1, which is 76 percent complete. The utility has repeatedly vowed to finish the project.

How much is Snow White worth? Such ungenteel speculation arose earlier this month amid rumors that Walt Disney Productions might be a takeover target. The rumors got a boost last week with the announcement that the Reliance Group has bought 6.3 percent of Disney. When any company is a possible takeover target, its assets are naturally a matter of keen interest. In the case of the movie studios, that means film libraries. Thus, when Rupert Murdoch, the Australian publisher, last year began his unsuccessful attempt to acquire Warner Communications, some analysts suggested that one of Warner's selling points was its film library.

A BILL now making its way through Congress, the reauthorization of the Vocational Education Act of 1963, is drawing attention to an area of education largely ignored by the many recent reports that have emphasized academic preparation for college. The bill is a reminder that programs to provide students with occupational skills are a major feature of high schools and community colleges. Millions of students, whether they are preparing to be secretaries, auto mechanics, commercial artists, dental hygienists or computer programmers, take at least some of their courses in vocational programs. At stake in the reauthorization of the act, which expires in September, is the way the states and local school districts will spend the approximately $750 million that Washington allots each year for vocational education.

''I hope to carry out a dignified, thoroughly professional investigation.'' - Jacob A. Stein, the independent counsel who will investigate accusations against Edwin Meese 3d. (A21:2.)

Three Arab terrorists armed with guns and grenades attacked crowds of shoppers in the heart of Jerusalem, wounding 48 people, one of them critically. Israeli shopkeepers and pedestrians fatally wounded one terrorist, and the police said the two others were captured. Some officials said the attack was the most brazen terrorist action in the city in memory. (Page A1, Columns 1-2.) Iran can produce chemical arms and may retaliate if Iraq continues its use of such weapons, Iran's delegate to the United Nations said. The delegate, Rajai Khorassani, said 40 Iranians have died as a result of Iraq's use of chemical weapons. (A12:3-4.)

Saying New York City had been ''shortchanged'' by $60 million, Mayor Koch warned yesterday that the new state budget would mean ''fewer police officers, teachers, parks workers, street repairers, street cleaners and others to provide essential services.'' The Koch administration had been counting on $200 million from Albany in order to balance the city's budget for the fiscal year that begins July 1. But the Mayor said the State Legislature had set aside only $140 million in the budget it passed Saturday.

The Supreme Court, reaffirming its rulings that organized prayer in public schools violates the Constitution, agreed today to decide whether ''moment of silence'' laws are unconstitutional as well. The decision, announced in a brief, unsigned order, appeared likely to shift the focus of the debate over school prayer from Congress back to the Court. Last month the Senate defeated two proposed constitutional amendments, one to permit silent prayer in the public schools and one that would have allowed officially sponsored, vocal prayer. In decisions in the early 1960's the Supreme Court barred such prayer.