Royal Watch: First Lady Nancy Reagan is going to the big wedding. That, of course, would be the wedding of Prince Andrew to Sarah Ferguson, which Buckingham Palace is constantly pointing out will not be anywhere near the size or grandeur of the one almost five years ago when Charles and Diana married. But then Charles will be king one day and Andrew probably won't.

Heads of state have not been invited to the July 23 wedding in Westminster Abbey. Nancy Reagan received a personal handwritten note from Prince Andrew asking her to attend, and she has accepted with her own note, her press secretary Elaine Crispen said yesterday. The president won't be going. He didn't attend Charles and Diana's wedding either.

Crispen said the first lady will not be deterred by the terrorist attacks in Europe, just as she was not deterred during her recent trip to Thailand and Malaysia. It hasn't been decided when she'll leave or where she'll stay while in London. The last time she stayed at the American Embassy residence.

End Notes

Hospital Reports: The Rev. Ralph David Abernathy, close friend and aide of the Rev. Martin Luther King Jr. during the turbulent years of the civil rights movement, is in satisfactory condition in Atlanta's Crawford Long Memorial Hospital. He was hospitalized after suffering a stroke. Abernathy, 60, who was named president of the Southern Christian Leadership Conference after King was assassinated in 1968, served in that role until 1977. He suffered an earlier stroke in 1983 and underwent brain surgery at Johns Hopkins University Hospital in Baltimore . . .

Former senator Paul Tsongas says his lymph node cancer is 95 percent arrested and he will undergo bone marrow treatment to try to cure what remains. In an interview in the Boston Herald Tuesday he said, "There's a chance for a cure, and we figure I should try it." Tsongas has been undergoing chemotherapy since 1984, when he decided not to seek reelection to a second term. He is expected to undergo the bone marrow treatment at Boston's Dana Farber Cancer Institute at the end of the month . . .

Rep. Robert Davis, who suffered a mild heart attack last weekend shortly after a morning jog, staged a telephone news conference from his Fairfax Hospital bed yesterday to say he would be back to work in a week or so and that he would conduct a vigorous reelection campaign in the fall. "I always could run circles around anybody else. And I still will be able to," he said . . .

One of Chicago's living landmarks, longtime Chicago Sun-Times columnist Irv Kupcinet is about to become a permanent landmark. A plaque will be unveiled today renaming the Wabash Avenue Bridge in front of the newspaper the Irv Kupcinet Bridge. Kupcinet, 73, has been writing his famous column since 1943 . . .

Walter Keane and Margaret Keane, whose paintings and reproductions of paintings of big-eyed children and animals were sold in furniture stores across America, have been in a court battle. Ordered by a jury to pay his former wife $4 million for slander in a dispute over the paintings, Keane says he will appeal. She sued him when he told a reporter his ex-wife was claiming to be the originator of the paintings he created because she thought he was dead. At one point Margaret Keane painted one in the courtroom, while her former husband declined, saying he had a shoulder injury . . .

President and Nancy Reagan will be at Sunday's "A Festival at Ford's" black-tie star-studded gala, which will be taped by CBS for broadcast June 25. Among the other political celebrities expected are House Speaker Tip O'Neill, Secretary of State George Shultz, Chief Justice Warren Burger, Secretary of Defense Caspar Weinberger, Sen. Paul Laxalt, former Senate majority leader Howard Baker and USIA Director Charles Z. Wick . . .

Mark Thatcher, son of British Prime Minister Margaret Thatcher, was pressured to leave his posh Dallas apartment because of threats on his life following America's British-backed raid on Libya. Thatcher, who reportedly moved to Dallas to be close to his girlfriend in Fort Worth, is at an undisclosed location where State Department agents are protecting him . . .