The Senator Theater observes its 52nd birthday tomorrow with a showing of Frank Capra's ''Mr. Smith Goes to Washington,'' first released in 1939, when the Senator opened. The price, for tomorrow only, will also return to 1939. Patrons will be admitted for 25 cents, which was the cost of admittance to the theater 52 years ago.
On Friday, the Senator will present, for one week only, ''Days of Heaven,'' the 1978 film starring Richard Gere, Brooke Adams and Sam Sheppard. This will be the first time the film will be presented in this area in 70 mm.
On Friday, Oct. 11, the Senator will begin a one-week showing of the 1957 classic, ''The Bridge on the River Kwai,'' then on Oct. 17, David Mamet's ''Homicide'' will open with a gala premiere screening with proceeds going to the Theatre Project.
The program will begin at 7:30 p.m. with the unveiling of a sidewalk block commemorating the occasion. This will be followed by a champagne reception.
The screening will begin at 8:30 p.m. Tickets are $25. ''Homicide,'' filmed in Baltimore, will remain at the Senator for three weeks.
The Towsontowne Dinner Theater production of ''Show Boat'' is a very uneven production. It needs tightening and focus, but it is very fortunate in having strong performers in the lead roles.
Dennis Knight, for instance, is Gaylord Ravenal, the riverboat gambler who marries Magnolia, daughter of Capt. Andy, lead man on the Cotton Blossom.
Knight is an ideal Ravenal. The man is supposed to be something of a stick, a well-dressed charmer, and Knight is that. He also has an excellent voice, which is why he appears so often in the local buffet houses.
When he sings ''Only Make Believe'' to Jane E. Brown, all the inadequacies of the production are forgotten.
They are also forgotten when Brown sings, along with Knight or along with Ann Alexander, who plays Julie, the singer who loves only one man, Bill. Alexander's ''Along Came Bill'' sounds very good, good enough to touch the spectator once again.
The Towsontowne ''Show Boat'' also sounds very good when all the players join for the ensemble numbers. When they do, ''Show Boat'' is a pleasure. Charles A. Johnson and Thomas V. Jackson are alternating as Joe, who sings ''Ol' Man River.''
Katie Horn is Kim, daughter to Magnolia and Gaylord. She, too, sings ''Only Make Believe'' with Knight, and once more, the effect is most pleasant.
The Towsontowne buffet, currently, is one of the best around. It, plus Knight, plus Brown and Alexander, make it worthwhile, maybe not enough to excuse the production's failings but enough to appreciate the evening, enough to send you out of the place humming one of the tunes.
''Show Boat'' will remain at the Towsontowne through Nov. 17.
The Towsontowne Dinner Theater will do an encore of its ''Italian Night'' on Oct. 14. Tickets are $18.95. The buffet dinner begins at 6:30 p.m., and the show starts at 8 p.m. Janet Crisalli and Arne Lindquist, members of the music faculty at Essex Community College, will sing, along with Ruth and Casper Vecchione. For more information, call 321-6595.
The Baltimore Actors' Theater, whose original ''Phantom of the Opera'' is now in its fifth year at the Oregon Ridge Dinner Theater, will soon have a rival production of the classic at Toby's Dinner Theater in Columbia.
''The Phantom'' is in public domain. There is nothing to prevent any group from doing a musical version of the play.
The BAT and Olney versions are not to be confused with the Andrew Lloyd Weber version that is playing in New York. The BAT version has its own score. Toby's version will also have its own score.
Frank Capra's 1947 film, ''It's a Wonderful Life,'' is also spawning a number of musical stage versions. Toby's did a musical version of the film last November, and now Washington's Arena Stage is planning a version for which Sheldon Harnick is doing the book and music, and Joe Raposo, the lyrics.