  Exoplanet imaging missions utilizing an external occulter (starshade) for
starlight suppression require precise alignment between the telescope and
starshade, necessitating maintenance of the starshade orbit during
observations. Differential lateral acceleration between the two spacecraft
serves as a proxy for fuel use and number of required interruptions to the
observation. Comparison against results from high fidelity simulations of
stationkeeping validates the use of this easy-to-compute proxy. Among starshade
positions constrained to the surface of a sphere centered about the telescope,
minima of differential lateral acceleration lie on a great circle and its
corresponding poles. We present a closed expression for telescope to star
vectors requiring minimal stationkeeping for observation from a telescope at an
arbitrary position
