Stargazing doesn't always involve the night sky in the Berkshires. Some head, instead, to the Williamstown Theatre Festival where Bradley Cooper, Gwyneth Paltrow, S. Epatha Merkson and many other famous actors take the stage regularly. They come here not just because there are few lovelier places to spend a summer than Williamstown, but because this theater has gained a reputation as an incubator for new works, both plays and musicals. In the last decade and a helf, over half-a-dozen shows have moved from here to Broadway, and far more have debuted here and then played theaters across the Unites States. Along with the mainstage, there's a smaller venue for more experimental works and a cabaret. The theater also puts on free outdoor shows for kids.