Foucault test question

Is there any reason why, if you know the ideal range of your test,
that you couldn't start at 70% of the mirrors diameter, and set your
dial at 50% of range and test each way from there?

I'm having a devil of a time precisely nulling the central zone, and
it is going to be behind the diagonal anyway.

Is there any reason why, if you know the ideal range of your test, that
you couldn't start at 70% of the mirrors diameter, and set your dial at
50% of range and test each way from there?

I'm having a devil of a time precisely nulling the central zone, and it
is going to be behind the diagonal anyway.

You are better off asking this on the atm list, but the short answer is it
doesn't matter where you start, as the readings are relative.

Dennis