An apparatus for measuring the azimuth of a tube having a bore axis includes a centering mandrel having a longitudinal axis; a flexible member for defining a bore axis projection of the bore axis; a tensioner fixed to one end of the flexible member, and a pair of adjusters connected to the tensioner, the adjusters for moving the tensioner along a respective pair of axes that are perpendicular to the bore axis projection, the axes of the adjusters being mutually perpendicular.