IF you think that museums, their cavernous halls filled with musty relics and awe-inspiring art, are the least likely places for merrymaking, think again. Boston's museums, which have long since erased most vestiges of stuffiness, have become a traditional part of the city's holiday celebration. Even the venerable Museum of Fine Arts flings open its doors during its annual ''Free-for-All,'' this year inviting the public to an open house of art, music, dancing, and children's events.
With the holiday season - and school vacations - already hurtling down upon the Hub, many of the city's museums have planned special exhibits for the family.
Stearns Hall at the Museum of Science is full of dinosaurs, including a full-size, animated brontosaurus. The exhibit, which continues until February, includes paintings and sculptures of dinosaurs, clippings from Hollywood's first dinosaur films, and cartoons.
''The Christmas Star,'' a program offering possible astronomical explanations of the Star of Bethlehem, will appear several times daily from Dec. 3-30 at the Charles Hayden Planetarium at the Museum of Science. For children, the planetarium will also show ''The Winter Wishing Star'' (complete with a trip to the North Pole) Friday and Saturday afternoons at 4 p.m. beginning Dec. 7.
If holidays are a time for family togetherness - but too often are spent in front of the television - take an outing to the Boston Children's Museum. On Sunday, the museum will hold a family workshop on dollmaking from 1 to 3 p.m., and on Dec. 2, it will host a workshop on gifts that children can make themselves (preregistration required).
December launches ''Celebrations Month'' at the museum, a look at how people in other countries celebrate their holidays. Each event will feature films, and food will be served that is native to Armenians (Dec. 1), Chinese (Dec. 2), Native Americans (Dec. 8), Filippinos (Dec. 15), and Poles (Dec. 23). In addition, the museum's annual ''Thank-you note clinic,'' complete with rubber stamps, will be held Dec. 26-28.
Ever seen a starfish's foot? You can see one, up close, as well as other marine life at a photo exhibit at the New England Aquarium. The pictures were taken with the Scanning Electron Microscope, which magnifies these organisms up to 50,000 times their normal size. Of course, the aquarium also has live animals - dolphins and sea lions perform daily and more than 1,000 fishes, sharks, and sea turtle swim in the Caribbean coral reef exhibit. During school vacation, Dec. 22-31, the aquarium will present special films and programs on penguins and puffins.
Music comes to the Boston Museum of Fine Arts during this year's Free-for-All , Dec. 7, 8, and 9. Traditional caroles, performed by Boston public high school choruses and the Boston Conservatory of Music, will be interspersed with more exotic musical selections: Leonard Solomon and his bellowphone, Peter Marston and his sea chanteys, and the Boston Shawm and Sackbut Ensemble playing Renaissance music, to name a few. Dancers from the Copley Square Ballet will practice their barre work outside the exhibition ''Edgar Degas: The Painter as Printmaker.'' For children who don't like to sit still, an Afro-American rhythm and games workshop will give them the opportunity to dance and improvise with shakers, drums, and rhythm block (Dec. 8 at 11:30 a.m. and Dec. 9 at 2:30 p.m.). Admission is free to the museum's ''holiday gift to all of Boston.''
Museum of Science
Open Tuesday through Thursday from 9 a.m. to 4 p.m., Friday 9 a.m. to 10 p.m. , Saturday 9 a.m. to 5 p.m., and Sunday 10 a.m. to 5 p.m. Closed Monday.
Admission is $5 for adults, $4 for students, $3 for senior citizens and children ages 5 to 16.
Science Park on Boston-Cambridge line via McGrath-O'Brien Highway. Parking at museum garage. Accessible by MBTA via the Green Line to Science Park Station.
Boston Children's Museum
Open Tuesday through Sunday, 10 a.m. to 5 p.m., Friday until 9 p.m. Closed Monday, except holidays. Closed Dec. 25 and Jan. 1.
Admission is $4 for adults, $3 for senior citizens and children ages 2 to 15. Free for children under 2.
300 Congress St. near Fort Point Channel. From the south, take Route 3 to the Atlantic/Northern exit. From the north, take Route 3 and exit at High and Congress streets. Follow signs to the museum. Parking available on Sleeper Street or Northern Avenue. Accessible by MBTA via the Red Line to South Station.
New England Aquarium
Open Monday through Thursday from 9 a.m. to 5 p.m., Fridays 9 a.m. to 9 p.m., and weekends from 9 a.m. to 6 p.m. Closed Christmas Day, but hours are extended during school vacation, Dec. 22-31.
Admission is $5 for adults, $3 for children ages 5 to 15, $4 for veterans, senior citizens, and students. Free for children under 5. Discounts on Friday after 4 p.m.
Boston's Central Wharf off Atlantic Avenue. Accessible by MBTA via the Blue Line to Aquarium Station.
Museum of Fine Arts
Open 10 a.m. to 5 p.m. Tuesday through Sunday, until 10 p.m. on Wednesday. The MFA's west wing is also open until 10 p.m. on Thursday and Friday.
Admission is $4 general admission, $3 if only the west wing is open, $3 for senior citizens. Free for MFA members and children ages 16 and under. Admission is free Saturday from 10 a.m. to noon.
465 Huntington Ave. Parking is available at the museum lot. Accessible by MBTA via the Green Line's E train to Museum/Ruggles Station.