t_Z = 0^h, δ_Z = φ,
t_Nd = 12^h, δ_Nd = - φ,
t_E = 18^h, δ_E = 0°,
t_W = 6^h, δ_W = 0°,
t_N = 12^h, δ_N = 90° - φ,
t_S = 0^h, δ_S = φ - 90°,