With the reflecting circle, one can sight three objects and measure two angular separations simultaneously (as two bright stars from the moon, for the lunar longitude method, or three coastal landmarks, for triangulation in coastal navigation). The example shown was 8" in diameter. Two mirrors were independently mounted at the center of rotation, each with a vernier arm and magnifier. One views through the adjustable sighting tube to the fixed mirror, then to the adjustable mirrors and to the targets.