What major optical limitation inherent in 19th-century refractor telescopes contributed to the subjective observation of faint Martian features?

Answer

Chromatic aberration

The text notes that the refractor telescopes used in that era were highly susceptible to chromatic aberration (color fringing) in addition to atmospheric distortion, which affected the clarity of faint planetary details.

What major optical limitation inherent in 19th-century refractor telescopes contributed to the subjective observation of faint Martian features?
HistoryMarsAstronomerobservationCanal