An autocollimator based optical system for precise angular alignment control over large exploring areas

An autocollimator based optical system has been developed which allows the relative angular positions of separate reflecting targets to be measured with high accuracy over a relatively large area. Misalignments suffered by the autocollimator head during translation between different measuring points are accounted for by utilizing a large plane reference mirror. Accuracies better than ±2 arcsec have been obtained over a 0.5 m diameter circular exploring area.