Predicted image quality for a long-exposure image (e.g., λ_LE) of a point-like source obtained using ground-based telescopes with diameters of 1.5 m (top), 8 m (middle), and 39 m (bottom), as a function of the wavelength. The panels correspond to different λ₀ conditions at 5000 Å: 0.4 arcsec (left panels), 0.7 arcsec (central panels), and 1.5 arcsec (right panels). Each curve corresponds to the indicated value of the ${ℒ}_0$ of the turbulence in meters: ${ℒ}_0$=100 → red, ${ℒ}_0$=32→ orange, ${ℒ}_0$=22 → olive green, ${ℒ}_0$=12 → purple, and ${ℒ}_0$=5 → lime green. The black curve follows the ε₀ wavelength dependence (ε₀(λ) ∝ λ^−1/5), corresponding to ${ℒ}_0$=∞. The solid curves correspond to the first-order approach to εLE following Eq. 5, while the dashed curves to the second-order approach considering the telescope diameter (Eq. 6). The dotted line delineates the ${ℒ}_0$/r₀>20 boundary, above which errors are constrained within ±1%.