The foulest sin in microscopy is to rack down with the coarse focus while ones eye waits at the ocular. -K
Always treat ones instrument with respect and consider the object upon the stage as well. Fine slides and delicate microscopes have come down through the years in such condition and numbers that even a casual enthusiast may have a first rate instrument and broad collection of slides at quite a reasonable price. It’s a terrible thing for such wonderful resources to become lost due to lack of observation of the microscopists obeisance.
When first placing a slide upon the stage orient a likely area beneath the objective and bow. There, with ones head low in deference to the care shown by others whose similar consideration permitted these items to persist long enough to become ones own, look askance towards the stage and rack the focus to set the objective within its focal distance. Then raise ones head and gaze into the eyepiece, hand upon the fine focus; never to touch the coarse unless one again bows low, for science and the preservation of history for generations to come.
Too many a wondrous specimen and unique objective have perished at the hand of the eager searcher, irreverent hand always upon the coarse focus and eye forever glued to the ocular. Why, just take a look at this poor eye:
A section, showing a retinoblastoma, spoiled by one to proud to take care. Balsam brittle and yellow it will still endure for ages but its perfection is spoiled by a crack (and missing portion) spanning the full length of the 30mm x 35mm cover. At least I can believe that the fool who damaged it learned his error-even at the cost of this slide-for the rest of the series I posses is thankfully free from evidence of such abuse.
So bow, low, and often! Save yourself and the slides in your care from damage such as this, take pride and make the microscopists obeisance!