For that reason we provide a monocular tube with our advanced scopes that lets the distance be varied. However, a few microscopes differ from this, and it is important to know the tube length of a microscope when ordering objectives. Finally, the very best objectives cannot make all of the corrections for aberrations by themselves. For that reason it is very important that one not mix the eyepieces and objectives between makers, or even, for example, between achromats and planapochromats from the same maker. We provide correcting eyepieces for use with the planapochromatic objectives that we sell.
Aberrations are also important for the condensor.
The first effective condensor was designed by Ernst Abbe, and bears his name. It is the condensor that is still provided with most microscopes. However, it has chromatic aberration, and it does not focus the light source on a single plane. Many other condensors have been designed, but most importantly, for use with planapo objectives, the condensor should be achromatic and aplanatic. We provide them as standard with our planapochromatic objective microscopes.