Note that the geodesic curve is transformed into graphical coordinate space for plotting, so that a straight line in physical coordinates may result in a curved line being drawn if the Mapping involved is non-linear. Any discontinuities in the Mapping between physical and graphical coordinates are catered for, as is any clipping established using astClip.
If you need to draw many geodesic curves end-to-end, then the astPolyCurve function is equivalent to repeatedly using astCurve, but will usually be more efficient.
If you need to draw curves which are not geodesics, see astGenCurve or astGridLine.
AST A Library for Handling World Coordinate Systems in Astronomy