Why should the microscope be calibrated for every objective and every use?

Question

please give concise answers and add links..tnx! :))

Answer 1

It isn't.  It's the lenses that are calibrated.  All lenses for a particular microscope need to be parfocal.  That means that the focus remains the same as you switch from lower to higher power lenses.  This keeps the image in focus.  In addition they need to be accurately centered.

Otherwise when you see something in low power and switch to high power the object willl no longer be in the field of view and will be out of focus so far that regaining focus wil be extremely difficult.