If the secondary mirror in a standard Cassegrain is not perfectly calculated for the primary, what specific aberration is likely to degrade star images?

Answer

Spherical aberration

Because the convex secondary mirror must correct the spherical aberration inherent in the parabolic primary, improper calculation of the secondary's hyperbolic shape can result in significant spherical aberration.

If the secondary mirror in a standard Cassegrain is not perfectly calculated for the primary, what specific aberration is likely to degrade star images?

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