FilmBy Lou GaulCaiktns Newspapers Film CnticBob Rafelson doesn't believe in playing it safe.With “Mountains of the Moon/' the director bites off more than he — or any filmmaker — can chew, and the result is an absolute joy to behold.For some reason, the sprawling R-ratea film has encountered indifferent audiences and lacklustre box-office results during engagements in other parts of the country, and it seemed that “Mountains of the Moon” might end up as just another video title.That would certainly have been a crime, since the wide-screen epic must be experienced on a big screen to be appreciated. Even though the story suffers from shortcomings, the picture remains a feast for the eyes from beginning to end.With Mountains of the Moon,” Rafelson follows the mid-1850s quest of Capt. Richard Francis Burton (Patrick Bergin) — the famed Anglo-Irish Victorian explorer, botanist, anthropologist, linguist and pre-Dr. Ruth sex expert — and Lt. John Hanning Speke (Iain Glen) — a member of the British aristocracy — for the source of the Nile deep in Central Africa.The picture raises questions about ambition, jealousy, opportunism, racism and colonialism. (The tide refers to the mountains that supposedly shrouded the Nile’s source.)Clearly, Rafelson, whose credits include Five Easy Pieces,” the remake of The Postman Always Rings Twice” and “Black Widow,” harbors no fear of weaving complex themes through this, astoundsepic tale. Though quite a bit to swallow, the film provides a satisfying feast for those willing to sample it.On the downside, Rafelson made some casting errors. Due to the sheer scope of the enterprise, the roles of Burton and Speke cry out for stars to carry them. (Mel Gibson and David Bowie were interested at one point.) He also plays with the facts about Burton and Speke in order to make the Irish explorer appear more heroic and the British traveler an opportunist with a villainous streak.But focusing on small details denies “Mountains of the Moon its resounding power.Obviously interested in overall impact, Rafelson provides stunning sequences — including a ferocious opening attack scene — and visuals of sprawling African landscapes as the tale deals with the destruction at the hiirriaii spine through obsession, dishonesty and jealousy.Rafelson presents his stunning “Mountains of the Moon” with an intensity and majesty rarely attempted by contemporary filmmakers more comfortable on sound stages or in safe location areas than in far-away places that pulsate with exotic thrills and unexpected dangers.MOUNTAINS OF THE MOONStarring: Patrick Bergin and fan Glen; produced by Daniel Melnick, screenplay by William Harrison and Bob Rafelson, based on the biographical novel 'Burton Speke by Harrison; directed by Bob Rafelson Running time: 135 minutes Parental guide:R rating (violence, sex, nudity).