Squared visibilities. The MBL is calculated for variations of 2%, 1%, and 0.5% (crosses, asterisks, and diamonds, respectively) as a function of three parameters. Top: stellar diameter with θ_p/θ_⋆ = 0.15 and (α_p = 0.2θ_⋆,δ_p = 0) mas. Middle: exoplanet diameter with θ_⋆ = 1 mas and (α_p = 0.2,δ_p = 0.0) mas. Bottom: spot temperature for θ_s = 0.15 mas and (α_s = 0.2,δ_s = 0.0) mas. The curves in the upper panel correspond to the analytical formula (see text). The curves in the middle panel correspond to the fit of Eq. (7).