On The Weekend Watch:
LOOKING BACK -- That's what two-out-of-three of NBC's late-night hosts are doing with specials tonight. First comes "The Tonight Show 29th Anniversary" (at 9:30, Channel 2), as soon-to-be-retired host Johnny Carson presents collections of highlights from the previous year's shows. And in "Tonight's" regular slot at 11:35, we get "Bob Costas: 3 Years . . . Later," a celebration of the third anniversary of the nightly wee hours show "Later with Bob Costas." In a cute touch, Dana Carvey and Phil Hartman are scheduled to do their Carson/Ed McMahon impersonations from "Saturday Night Live."
WHERE'S LETTERMAN? -- Left out of the specials, "Late Night" host David Letterman can be seen in his usual 1:05 slot. And here's a reminder that the Arts & Entertainment cable network has begun reruns of past Letterman outings at 7 p.m. weekdays.
WHODUNIT? -- Maryland Public Television offers a nice couple hours for mystery buffs tonight. First is the season premiere of PBS' "Mystery!" (at 9), with P.D. James' detective Adam Dalgliesh in the six-part "Devices and Desires." And at 10 is "Philip Marlowe: Private Eye," with Powers Boothe as Raymond Chandler's taciturn shamus in "Blackmailers Don't Shoot."
THE SPORTS SCENE -- TV can be the next best thing to being in Memorial Stadium Sunday for the Orioles' swan song in the park, soon to be abandoned. At 8 p.m. Saturday, Maryland Public Television is screening "Baseball: The Birds on 33rd," a new hour-long special about the ballpark. Two other half-hours, "Baseball's Heirlooms" (a tour of other venerable parks) and "Hardshell Hardball" (a 1988 special about baseball in Baltimore) follow. Channel 13 also has a Memorial Stadium special Saturday, "Diamonds Aren't Forever," (8 p.m.). And on Sunday, Channel 2's coverage of the final game includes a noon rebroadcast of last night's "Magic Moments at Memorial Stadium," a 1 p.m. special edition of "Orioles on Deck" and the 2 p.m. game with Detroit.
THE CABLE CONNECTION -- Two things new on premium channels and one amusing oldie for basic subscribers highlight the cable networks in the coming days. First on Friday (10:30 p.m. on Showtime) is "Elayne Boosler: Live Nude Girls," in which the observant comic wonders, among many other things, why men go to strip clubs. Also new on Sunday (at 10:10 p.m. on HBO) is "Sessions," a pretty funny but distinctly adult weekly series, created by Billy Crystal, in which Elliott Gould plays a psychiatrist and Michael McKean is his patient. As for what's old, it is "F Troop," the 1965-67 series that made it hard to believe the West was ever won. The Nick at Nite network launches weekly reruns of the Larry Storch, Ken Berry and Forrest Tucker series at 9 p.m. Saturday.