"Star Trek--the Motion Picture" opens today at approximately 900 movie theaters around the country; Paramount and Pocket Books hope that "Star Trek"--the fad--will open at the same time.

Sack 57 is the only movie theater in Boston showing the film, whose budget has been estimated at $42 million--the most expensive in film history. A spokesman for the theater said yesterday that Sack 57 has not sold advance seats, but added she does anticipate long lines. The theater has not increased security because the staff can handle the crowds, she said.

Clones

The popular series has spawned avid fans--"trekkies"--who number about 35 million, Joan C. Stanley, vice-president of the Boston Star Trek Association said yesterday.

Materialism

Pocket Books and Paramount are counting on those 35 million fans to snap up "Star Trek" paraphernalia. These include 17 different books, a soundtrack album and a "make your own Star Trek costume" book, Suzanne Gordon, publicity agent for Paramount, said yesterday.

Pocket Book titles include "Star Trek," the book of the movie; a Star Trek calendar and "The Official Star Trek Enterprise Officer's Datebook 1980." Deborah Gallagher, sales clerk for Harvard Bookstore, estimated sales of the novelized Star Trek at about 15 a week, an above average record.

Stanley said that she knows of more than 500 amateur Star Trek publications in the U.S. Star Trek has been translated into 52 different languages and shown in 30 countries, she added.