ON AND OFF THE AIR:
* Parents who are stern about no school-night television viewing might think about making an exception for "Avonlea," which returns for a third season to the premium-cable Disney Channel tonight (8 o'clock).
Like the beloved "Anne of Green Gables" series, the show springs from the short stories of Lucy Maud Montgomery, set in the turn of the century period on lush Prince Edward Island.
Actress Sarah Polley, whom viewers might remember from the film "The Adventures of Baron Munchausen" or the PBS series "Ramona," serves as the crux of the stories, an off-island city child sent to live with her country relatives.
And Disney recently announced that this season's adventures will include guest appearances by a number of well-known actors, including Christopher Lloyd ("Back to the Future"), Christopher Reeve ("Superman"), Kate Nelligan ("Prince of Tides") and Ned Beatty ("Superman").
* After a couple of weeks of pre-nuptial strife, Evan and Fontana (Hal Holbrook and Linda Gehringer) make it to the altar tonight on the CBS series "Evening Shade" (at 8 o'clock, Channel 11).
* A birthday party for Italian composer Gioacchino Rossini -- posthumous, of course, for it would be his 200th -- marks tonight's "Live From Lincoln Center" broadcast on PBS (at 8, on Maryland Public Television).
* The 1986 film "Top Gun," airing at 8 tonight on WNUV-Channel 54, zoomed to box office success and hugely boosted the careers of Tom Cruise and Kelly McGillis. But does anybody think the film was even remotely believable?
Besides, the stars are really those lovingly photographed twin-tail F-14 Tomcat jets.
* The basic cable show biz network, E! (Entertainment Television) looks over the Academy Award field in a one-hour special at 7:30 tonight, "E!'s Complete Guide to the Oscars." Film clips and interview snippets with the hopefuls are in the mix.
* Come November, officials at Baltimore's ABC, CBS and NBC network affiliate stations may check the overnight ratings of their shows as measured by the Nielsen Media Research ratings service "people meters," according to an announcement from the Nielsen firm.
WJZ-Channel 13, WBAL-Channel 11, and WMAR-Channel 2 have signed up for the service, as Baltimore joins Kansas City and San Diego among new cities being added in the fall to 25 other markets using the more sophisticated metered-market ratings system.