What specific aberrations primarily resulted from William Herschel tilting his massive primary mirror by 2 degrees?

Answer

Astigmatism and coma

Tilting Herschel's primary mirror to avoid placing the eyepiece in the light path introduced horrific off-axis aberrations, primarily astigmatism and coma.

What specific aberrations primarily resulted from William Herschel tilting his massive primary mirror by 2 degrees?
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