Simon,
I began reading your 2018 hardcopy version that I have this morning from page 1.
The Shack-Hartmann principle and adaptive optics AO paragraph was of special interest to me. I took your advice and read the wiki entry.
(any relation to Roland? ; )
The wavefront sensor measures the distortions the atmosphere has introduced on the timescale of a few milliseconds the computer calculates the optimal mirror shape to correct the distortions and the surface of the deformable mirror is reshaped accordingly.
I seem to remember a recent long exchange you had with someone, it might be here on this forum or the Historical Astronomy forum, who kept insisting that the aberration of light theory made your argument spurious.
So after reading about Adaptive Optics, can we not finally dispense with the aberration of light subterfuge? Or am I completely off base?