Cable TV offers some choice viewing before the networks' new season

Have you just about given up TV this summer because of the dearth of acceptable fare on the commercial networks? Well, perhaps now is the time to look toward cable TV.

Close to 30 million homes - with around 85 million people - are now wired for cable TV, and the month of September, before the commercial networks begin their season at the end of the month, represents fine viewing time. There are some sugarplums in store for you on several of the cultural-entertainment channels, some pay and some free.

The main problem is to make certain a basic cable system carries the particular service in which you are interested and then to pinpoint the service on your dial, something that is becoming more difficult as cable channels and services proliferate. The easiest way to overcome these handicaps is simply to call the manager of your local cable service and ask about the service you want. If the system is not carrying the service, ask that it be started. Cable systems are still small enough to be influenced by individual viewer requests.

Here are just a few selected highlights from the programming available in September on cable TV: ARTS CHANNEL (free)

Joan Sutherland: A Life on the Move (Sunday, Sept. 5, 9 p.m.; repeated Thursday, Sept. 9). Behind the scenes at the Metropolitan Opera House in New York, the Sydney Opera House in Australia, concerts in Japan and Korea, recording sessions in London, and at home in Switzerland. Excerpts from ''Norma, '' ''La Traviata,'' ''Don Giovanni,'' and ''The Merry Widow,'' as well as new insights into the life and character of this famed diva.

The Grand Age of the Gardens (Monday, Sept. 6, 10:20 p.m., repeated Friday, Sept. 10). A slightly precious but still delectable truffle of a documentary, unearthed from the flower gardens of the world throughout history. The elements of landscape architecture and garden design are presented with fragrant and picturesque examples.

The Charterhouse of Parma (premieres Tuesday, Sept. 21, 10:45 p.m., Eastern time; continuing Saturday, Sept. 25; Tuesday, Sept. 28; Saturday, Oct. 2; Tuesday, Oct. 5; Saturday, Oct. 9 p.m.). This six-part miniseries adaptation of Stendhal's 19th-century novel, produced by a European consortium, stars Marthe Keller and Andrea Occhipinti. ARTS is rushing the series to the cable to beat PBS, which starts airing it in mid-October.

Tennesee Williams (Tuesday, Sept. 21, 9 p.m; repeated Saturday, Sept. 25). The life and work of Williams, including excerpts from ''A Streetcar Named Desire'' and ''The Glass Menagerie,'' acted by Maureen Stapleton and Joss Ackland.

Macbeth (Tuesday, Sept. 28, 9 p.m.; repeated Saturday, Oct. 2). Philip Anglim of ''Elephant Man'' fame plays Macbeth in an offbeat production that marks the directorial debut on cable of Boston Opera's Sarah Caldwell. THE ENTERTAINMENT CHANNEL (pay)

The Day of the Triffids (premieres Sunday, Sept. 5, 8 p.m., with two more episodes scheduled for successive Sundays at 8 p.m.). A BBC three-part miniseries adaptation of John Wyndham's near-classic science-fiction thriller about a future world gone berserk.

Sweeney Todd (Sunday, Sept. 12, 8 p.m.). Tony Award-winning musical drama about a 19th-century Fleet Street barber who takes revenge on those responsible for his unfair imprisonment . . . and on society, as well. Angela Lansbury, who starred on Broadway and on tour, repeats her role in this Stephen Sondheim opera/musical comedy, already being called a classic.

The Boat Is Full (Saturday, Sept. 18, 9 p.m.). This film, one of 1981's best, directed by first-time Swiss director Markus Imhoof, is a biting attack upon the Swiss handling of Jewish refugees during World War II. The film played in a few big cities for a few weeks and disappeared. Now, the Entertainment Channel is performing a public service by reviving it.

The Wings of the Dove (premiered last Sunday and to be repeated at selected times throughout September) and Jessie (Sunday, Aug. 29, 8 p.m., and to be repeated throughout September). BBC specials that are really something special. ''Dove'' is a Henry James tale about the misadventures of a rich American heiress abroad, starring Lisa Eichorn. ''Jessie'' is a poignant picture about love and respect between two social outcasts. Both are superbly literate viewing. CBS CABLE (free)

A Walk Through the 20th Century With Bill Moyers (premieres Wednesday, Sept. 8, 8:30 p.m., and continues for 19 more Wednesdays. Check local listings for alternative times in many localities). Moyers, the ubiquitous ''conscience of American TV,'' puts the immediate past into proper current perspective. A landmark series which by itself catapults CBS Cable and its producer, the Corporation for Entertainment & Learning, into the front ranks of TV documentarians. USA CABLE NETWORK (free)

Einstein: The Man Behind the Genius, followed by Continuum: The Special Theory of Relativity (Sunday, Aug. 29, 12 noon, repeated at various times throughout September); both presented by the English Channel. First, a one-man show by Steven Polinsky, who portrays the genius of Einstein the man and Einstein the scientist. Then, a glorious one-hour educational special by the National Film Board of Canada which makes Einstein's theory almost understandable.