It;s safe to assume that almost any telescope and eyepiece
is far better than the night sky when seeing is bad.
That means...don't worry about inside the scope,
other than focus. The seeing is worse.
Correcting for atmospheric disturbance is parking
the focuser at the best average....if the turbulence
is high up (most common).
Correcting for "rounder" and longer lasting disturbances
would mean you could chase the best focal position.
The fact that you can chase focus at all means that
a disturbance is fairly close (100--1000 ft)....
making the apparent location closer---nearer-closer.
So...ordinary depth of in-focus would predict how the
focuser has to react. Long and short scopes would
have trouble, but the higher f-ratio would be in focus over
a longer range in that near-field distance....like a camera
And...less sensitive to the focuser, of course.
At the center of a hot parking lot would be the best spot
to be less disturbed. At the edges, the rising air
would be more turbulent, and you would be looking
into it sideways....the worst possibility.
Edited by MartinPond, 31 July 2019 - 05:56 AM.