This was applied to an excellent achromatic telescope of 34 in.
It will be seen, then, that the visual and photographic foci are now merged in one, and the image is practically as achromatic as that yielded by a reflector.
If not, the substitution of an achromatic lens will be of no advantage.
Especially powerful achromatic condensers are really only magnified microscope objectives, with the difference that they are not corrected for the thickness of the cover slip, but for the thickness of the glass on which the object is placed.
He also succeeded in constructing an almost perfectly achromatic eye-piece, still known by his name.