Orbital elements of binary components in a hierachical system can be fit to either the visibility data directly or to the separation and position angle data. ... Then use Data|Astrometry to read a previously prepared file ("zetuma.psn") containing the positional data. ... Semi-major axis = 8.4214471 . Semi-minor axis = 4.7663976 . ... We can now use the Thiele-Innes method to estimate the orbital elements from this apparent ellipse and the data, as implemented with the Util|Orbit button. ...