How to test a new to you microscope objective

[Scoper]

So how does one test a new to you microscope objective?

Thanks

[apochronaut]

For diascopic objectives always use a prepared slide as a standard : either one you know very well or one that has known parameters, such as a diatom test slide.When possible, compare the objective to a similar one you are familiar with, even if that means changing eyepieces or setting up two stands side by side. The optical train used for the new objective needs to be compatible with the objective. Tube length, relay optics and eyepieces.

[apochronaut]

I should have added to the above but I guess I thought it would be obvious, that if you are comparing two objectives from different systems, a 40X .65 planachromat from a 160mm system for instance to a 40X .65 planachromat from an infinity system and therefore have to use two sets of supporting optics, that the illumination systems need to be optimized in each case and if possible be the same type.

[blekenbleu]

Before installing in a microscope, I hold new objectives near a computer monitor, with the bottom closest to the screen.
With minor fiddling, one should see crisp RGB subpixels from white display areas.
This quickly sorts optics needing attention, e.g. dried oil removal.
First target on microscope will be a calibration slide, with or without cover slip, depending on objective design.