Ghostlight inhabits territory all its own: Call it “schlock doc.” Christopher Herrmann, a former associate of the Martha Graham Dance Company and its diminutive diva, met Richard Move, the six-foot-four drag queen who channeled the choreographer in the priceless cabaret series “Martha@Mother.” Both men adore Graham (who died in 1991, just shy of 97) and mock her foibles, but their film falls on its own sword. Ghostlight, made without cooperation from “the Graham entities,” boasts mock-doc footage of Move with Rob Besserer playing Graham’s partner, husband, and rival, Erick Hawkins. The Merce Cunningham Studio stands in for Graham’s East Side townhouse. Real history and raunch poke through, but the thirtysomething Move is too vital to be Martha in her dotage. Amusing for insiders, Ghostlight may confuse everyone else.