Remarks on Orbits and Dynamical Parallaxes

Extract

In connection with statements made at the preceding session, some results presented at the Nice Conference on systematic and random errors affecting the elements a and P as well as a³/P² may be recalled. If many orbits have been calculated for one binary, it is instructive to plot log P, log a, and log a³/P² versus log Δt/P where Δt is the time interval covered by observations. As a general rule, when Δt ≃ P the systematic trends vanish, and the scatter of the plotted elements reaches a low value, not considerably changing thereafter. It may well be of interest, then, to have several orbits based on the same observations but computed by different authors and methods.