What's the highest magnification you use on a microscope and why?

[jpanhalt]

what microscope can do like 100x without a white cloud starting to show up in the picture? its useful for various things like PCB sides, connectors, etc. but a electronics one needs a huge base to be useful at that range (rail system)

Do you mean 100X objective (resolving power) or 100X total magnification?  Presumably, you are asking about viewing opaque objects, not transmission microscopy.  The working distance for a 100X objective in a typical microscope is quite small, e.g., negative in air, which is why oil immersion is used.

For total of 100X magnification, you can use a 5X objective and 20X eyepiece.  Some dissection/inspection microscopes may do that.  Mine only goes to 4X objective.

[coppercone2]

well maybe not 100x, but at high zoom, its usable but there is white fog. oil is not really practical in this situation. I figured its just a consequence of such high zoom. It stops being 'nice' at like 40x.

Say looking down from the top on a BNC connector center pin hanging in a arm off the side of a table (held in small helper hand), for microscopes on big articulating arm/rails (heavy, big and hard to adjust... you gently tap them to get the image centered after the screws are tightened lol)

actually better way to describe it might be a off blue/yellow haze, not white fog, and they are always stereo (for electronics)

[Phil1977]

That may be a bad case of out-of-focus-chromatic-aberation. This frequently happens with optical systems that are better specified than they really are - like all these toy microscopes and telescopes with astronomic magnifications for little money.

I don't say that yours is *such* a bad design, but with a really good design a flat target (e.g. a money bill or better some IC die) stays sharp and crispy over all available magnifications.