Question

which adjustment knobs are used when focusing at low or high magnification?

Answer 1

You would want to use the fine adjustment knobs (or whatever you call the-- not coarse knobs) if you are working in both high and low. Generally you want to use coarse to find the specimen in low mags and then use fine to adjust the view when you move to the higher mags

Answer 2

for scanning and 10x magnfication use the coarse adjustment knob while 40x and the oil immersion use the fine adjustment knob.. i hope this helps.