Azimuth circle by Edward Troughton A repeating altitude azimuth circle, comprising a vertical axis, an azimuth circle, an alatazimuth mount and two telescopes. The altazimuth mount allows the telescopes to move along the vertical (altitude) and horizontal (azimuth) axes to aid the mapping of the stars. Manufactured by Edward Troughton and taken to India by Henry Kater for use in the Great Trigonometric Survey. early 19th century