FOREST J. ACKERMAN, the man Bella Lugosi called "Mr. Monster," will be in town this weekend signing autographs and talking about horror films.

The 69-year-old former editor of the now-defunct monthly Famous Monsters of Filmland magazine is considered an authority on horror and science fiction films. He's had acting roles in dozens of horror films over the last 40 years, including such recent productions as The Howling, Dracula Vs. Frankenstein, plus a bit part in Michael Jackson's Thriller video.

Ackerman lives in a 17-room Los Angeles mansion filled with more than 300,000 movie artifacts, including the spaceship from War of the Worlds, the wrappings from Boris Karloff's mummy, the cape that Claude Rains wore in The Phantom of the Opera, and Bella Lugosi's silver bat ring.

Some items from his collection -- among them a copy of the Capitol Dome that was used in the 1956 Earth Versus the Flying Saucers, and a poster from the 1935 Phantom Empire -- are now on display at the new "Hollywood: Legend and Reality" exhibit at the Museum of American History. (A review of the exhibit appears on Page 41).

Fans can see Ackerman Saturday at the Video Vault in Old Town from 10 to noon where he'll be signing autographs and talking about movies. Call 549-8848 for information.

The Video Vault, at 706 Duke Street, specializes in cult and off-beat movies.

"We've probably got more than a hundred movie titles that you won't find anywhere else in town," figures store owner Jim McCabe, who lists among his inventory such hard-to-remember and hard-to-get films as The Naked Kiss, Edgar Ulmer's 1946 Detour, and Ed Wood's Plan 9 From Outer Space.

Ackerman will also be interviewed during Channel 20's weekly "Creature Feature" this Saturday night. This week's film, The Brain That Wouldn't Die made in 1963, begins at 11:30 p.m.

The theater bonus of the week may be at the American Film Institute on Saturday at 7 and Tuesday at 6:30 during screenings of Casablanca. In addition to Humphrey Bogart and Ingrid Bergman, you'll be treated to a look at some of Washington's forgotten movie palaces in Theaters Dark, a 5-minute production by local filmmaker John Heyn who made the 16mm documentary in 1984 with only $700. Highlighted are such lost or obscure theaters as the Tivoli at 14th and Park Road, H Street's the Atlas, the Langston on Benning Road (now the site of a Kentucky Fried Chicken store), the Penn Theater (only the facade remains), Mount Rainier's Kaywood and even the Lee Highway Drive-In. If the film sounds a bit familiar, you may have seen it at the Biograph's "Expose Yourself" filmmakers competition two years ago or the Hirshhorn Museum. For AFI ticket information, call 785-4601.

Donna Deitch's low-budget lesbian romance film, Desert Hearts, may prove once again that you don't always have to spend much money to make money.

"Desert Hearts," which cost slightly more than $600,000, was shot on location in Nevada in a brisk 31 days during August 1984 with almost no extra takes. "We re-did one car-mount shot," says producer and director Deitch. "But other than that, if we didn't get it, we didn't get it."

Despite mixed reviews in New York, where it opened two weeks ago, the film has been raking in money at Manhattan's 290-seat Cinema II Theater, an astounding $36,289 during its first week and an additional $23,455 the first five days of this week.

Roughly $250,000 of the film's budget was spent on the soundtrack, with nearly a dozen songs by such artists as Patsy Cline, Buddy Holly, Elvis Presley and Ella Fitzgerald.

"Roadwork," the non-profit Washington-based cultural group that promotes women artists, will introduce the film here on Friday at a 7:30 benefit screening at the West End Theater and hold a reception afterward at C'est La Vie restaurant. The organization, which has produced the two-day "Sisterfire" music festival in Takoma Park in years past, plans to use money from the screening for the next festival. Tickets for the screening and reception are $15. For purchase locations, call 234-9308.

You can screen your latest homemade 3/4-inch video, Super 8 or 16mm movie this Monday at 8:30 at the bimonthly meeting of I Am Eye, Washington's loose-knit film club. Representatives from Virginia cable Channel 33 will be there to view members' works and talk about their station's video production workshops. Among the videos scheduled to be shown at D.C. Space (Seventh and E streets NW) are Madhouse Mecca Video, Man in a Cage, Cow's Confession, Rockin' Objects and videos of several local bands. I Am Eye meets on the first and third Monday of each month at D.C. Space. Cost is $1 or one film. Call 667-6498 for details. SHORT TAKES -- The Global Assembly Line, produced and directed by Washington's Lorraine Grey, screens twice on Sunday to benefit the Philippine Support Committee, Washington Forum on the Philippines and Church Coalition for Human Rights in the Philippines. The documentary examines the daily grind of working men and women on labor-intensive assembly lines in "free trade zones" as manufacturers close their operations in the U.S. and search the world for lower-wage workers. The film was shot in the U.S., Mexico and the Philippines. Tickets are $6, with showings at 1 and 3 at Georgetown's Biograph. Call 332-0961 for advance sales.

Also on Sunday, the Polish Film Discussion Group will sponsor the 2 p.m. screening of Nights and Days. The 150-minute Jerzy Antczak production, sometimes called Poland's "Gone With the Wind," stars Jadwiga Baranska and Jerzy Binczycki. The screening, in Polish with English subtitles, is free at the Arlington Library, 1015 North Quincy Street, near the Virginia Square Metro stop. Call 527-4777.

The Martin Luther King Jr. Library continues its free series on American architecture on Tuesday evening at 6:30. The featured architect is Mies van der Rohe, who, incidentally, designed the library at 901 G St. NW. The 60-minute program is free. Call 727-1271.

In Baltimore, the Walters Art Gallery begins its five-part "Entering the Medieval Mind" film series on Wednesday with The Christian Empire and Simon of the Desert, both directed by Luis Bunuel. The series coincides with the "Silver Treasure From Early Byzantium" exhibit on view until August 17. The projector rolls at 8 in the Graham Auditorium; tickets are $6 for Walters Art Gallery members and $8 for non-members. The gallery is at 600 North Charles Street. Call 301/547-9000.

On Thursday evening at 8, the Hirshhorn Museum begins its free spring film series with Alan Rudolph's Return Engagement, a documentary on the absurdities of pop celebrity in American culture. The screening repeats the next evening at 8. Call 357-2700 for a complete spring schedule.