Fig. 8

Theoretical Strehl ratios for the Ca ii H filter, calculated by integrating the MTFs. The pupil functions at each wavelength are calculated without the phase, with the phase, and with two different compensations for the phase. Φ4 is an optimum focus term, while Φ11 is an optimized sum of focus, astigmatism, coma, trifoil, and spherical aberrations.
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