Elliptical coordinate system (ξ, η) consisting of the confocal family of parabolas, η, and ellipses, ξ, depicting the electric field and potential, respectively, of a negatively charged elliptical dust grain in a plasma. The blue ellipse and the circle represent the surface of the dust grain and the plasma sheath, respectively, and the red curve signifies the parabola with asymptotes θ = ±π/4.