What innovation solved the problem of chromatic aberration by the mid-18th century?

Answer

The achromatic doublet.

The achromatic doublet design, developed by combining lenses made from different glass compositions, was the breakthrough that dramatically reduced the colorful halos by bringing two specific wavelengths to a common focal point.

What innovation solved the problem of chromatic aberration by the mid-18th century?

#Videos

What Are Two Disadvantages Of Refracting Telescopes? - YouTube

HistorytelescopeaberrationrefractorOptic