How is spherical aberration typically corrected in modern, high-quality refractors?

Answer

By shaping the lens surfaces into a non-spherical, or aspheric, profile.

While spherical aberration is inherent to spherical shapes, it can be mathematically compensated for by grinding the lens surfaces into an aspheric curve, though this process is technically demanding.

How is spherical aberration typically corrected in modern, high-quality refractors?

#Videos

What Are Two Disadvantages Of Refracting Telescopes? - YouTube

Ch. 6: Telescopes (10 of 25) What Are the Limitations of ... - YouTube

astronomytelescopeLenslimitationrefraction