altazimuth

It resembles an astronomical altazimuth, but instead of a telescope it carries an open tube without any lenses.

The altazimuth can thus determine the altitude and azimuth of objects, hence the name.

On his return home he settled at Westbury, where he erected an altazimuth by Troughton, with a two-and-a-half-foot circle.

This pillar is the support of Airy's altazimuth, and very nearly marks the place where Flamsteed set up his original sextant.