Geometry of the umbral, antumbral, and penumbral shadow cones, when star S is eclipsed by body A, casting a shadow on body B. The shadow cast by A into space is rotationally symmetric around the axis through the center of the star and body A. The radii of the star, body A, and body B are denoted by R_S, R_A, and R_B, respectively. Points O₁, O₂, O₃, O₄, and O₅ denote auxiliary points: the umbral and antumbral cones have apex O₁ and aperture2Ψ and the penumbral cone has apex O₂ and aperture2Ω. The lower figure also shows angles ζ, ρ, ω_i, β_i, and θ, that are used in the computation of the eclipse shadow depth. Distances between bodies and radii are not to scale in order to emphasize the geometry of the system.