ROCKLAND — The Rev. Dr. Ralph M. Moore Jr. will be the 14th rector of St. Peter’s Episcopal Church, beginning Sept. 1. Moore is acting dean of student and community life at the Episcopal Divinity School, Cambridge, Mass. He also was visiting priest at Dorchester Abbey, Oxfordshire, England, and served as priest-in-charge at All Saints’ Episcopal Church, Stoneham, Mass., after missionary work in Costa Rica and Nicaragua.