Royal Watch: No more counting necessary. With Samsonites gripped firmly in hand, Charles and Diana arrive tomorrow morning at Andrews Air Force Base. After their lengthy visit to Australia, where they actually got to meet the natives, Washington will be quite different. Everything here is so carefully orchestrated and formal that the royals probably will go home with the idea that most Americans dress like characters in "Brideshead Revisited."

There is little chance that Diana will have an experience here similar to one in Canberra yesterday, where she and her husband visited a construction site and the workers wolf-whistled appreciatively at her. One of them, bare chested, wearing shorts and with a T-shirt around his head, engaged Diana in conversation. He said she wasn't at all snobby and that she told him she liked his hat . . .

The royal visit even has ramifications in a fight over the firing of a librarian at a private library in Northeast Harbor, Maine, where many of the wealthy summer. Radio stations WWMJ and WDEA of Ellsworth and Bangor, owned by former St. Louis Post Dispatch bureau chief Richard Dudman and his wife Helen Sloane Dudman, report that members of the private library board from Philadelphia, Fifth Avenue and Palm Beach are expected for a Saturday meeting to settle the spat. However, that is not a good date for Brooke Astor. She has complained bitterly by letter that that is the one day she can't be there. She has to be at the White House that evening to dine with Charles and Diana. That seems an acceptable excuse, and now we know another name from the closely guarded White House guest list. If you want to see superstar Tom Selleck, he's expected to be dining there that night also. A New Magazine for Dads

Jeff Stein, founder of now-defunct Washington Weekly and the former editor of City Paper, is about to start a new magazine, Fathers: A Magazine for Men. Stein, who is president of the new venture, has announced that Harry Stein (no relation), longtime "Ethics" columnist for Esquire magazine, will be the editor. Life magazine's Bob Ciano is designing the new publication, and Duncan Spencer, author and former Washington Star reporter, will be the Washington articles editor. Among the contributing editors are well-known writers Ken Auletta and Dan Greenburg as well as Time magazine film critic Richard Schickel.

Jeff Stein said yesterday that the magazine, which he expects to begin publishing in the spring, will target first-time fathers. The magazine will have father-son, father-daughter features such as "Should He Be Playing With Dolls," "Sons of Superachievers," "Child Care Manuals: Most Useful and Best Kindling" and "Dealing With a Son Who Is the Last One Picked." End Notes

Millionaire Malcolm Forbes had a farewell party for his famous and well-used yacht, The Highlander. He's retiring it for a still bigger and better one. Joining the sail around Manhattan Wednesday night were former chief of protocol Henry Catto and his wife Jessica, publisher of the Washington Journalism Review, former White House aide Mike Deaver and his wife Carolyn and former Sen. Abraham Ribicoff and his wife Lois. A surprise guest, in town without the great fanfare other members of the family cause, was Princess Margaret . . .

President Reagan presented the Medal of Freedom yesterday to veteran arms negotiator Paul Nitze and the husband-and-wife team of national security experts, Albert and Roberta Wohlstetter, who were among President Kennedy's advisers during the 1962 Cuban missile crisis . . .

Ladislav Bittman, who defected from the Soviet Union in 1968 after 14 years as a Czechoslovak intelligence operative, was back in town this week promoting his new book, "The KGB and Soviet Disinformation: An Insider's View." Because of the Vitaly Yurchenko turnaround, Bittman has found more interest in his book than there might have been and has been making the rounds of the usual talk shows. In a phone conversation yesterday, Bittman said he didn't believe Yurchenko was a double agent or that he was drugged or kidnaped by the CIA. Bittman said debriefing is a "deep psychological trauma . . . a very traumatic experience," and believes that Yurchenko "just gave up" . . .