Precession model applied to the component C5 of 3C 279. We assumed that the time origin is 1998.80 ≤ t_o ≤ 1999.10. Top figure: the function χ²(i_o) is limited to 0.8° ≤ i_o ≤ 4.3° and has no minimum in this interval. It stops at i_o ≈ 4.3° and i_o ≈ 0.8° because at these points the bulk Lorentz factor becomes larger than 30. Bottom figure: the bulk Lorentz factor diverges when i_o → 4.3° and i_o → 0.8°.