Absolute quadrant determinations from speckle observations of binary stars

Vector-autocorrelation techniques are highly suited to extracting astrometric information from very large volumes of speckle data in near real time, but they inherently introduce a 180-deg ambiguity in the position-angle measurement. This can be a problem in determining the orbital motions in binaries, so an algorithm is presented which maintains most of the simplicity of vector autocorrelation while removing the quadrant ambiguity. Results are provided from absolute-quadrant determinations for 66 binary star systems first resolved by the long-term GSU/CHARA speckle program. The algorithm is used to eliminate the period ambiguity in the orbit of the close visual binary ADS 9744.