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 AST_CLIP.
If you need to draw many geodesic curves end-to-end, then the AST_POLYCURVE routine is equivalent to repeatedly calling AST_CURVE, but will usually be more efficient.
If you need to draw curves which are not geodesics, see AST_GENCURVE or AST_GRIDLINE.
AST A Library for Handling World Coordinate Systems in Astronomy