Compound achromatic microscope, stand I

Description

This microscope has a brass horseshoe foot, filled with lead. On the foot two brass pillars supporting the limb via trunnions. The simple rectangular stage is covered with a sheet of phenolic paper instead of the original ebonite. There is a substage holder for a condenser, which is however missing. The mirror is adjustable in a bracket. Coarse focussing is by rack and pinion on the body tube, fine adjustment is by means of a micrometer screw in the side pillar. The body tube is adjustable between 138 and 193 mm. The microscope has a triple rotating changer, provided with the old Leitz thread.
There is only one eyepiece present, a Leitz ‘Periplan OK 12×’, which is of a later date.
The three objectives are original, they were investigated using the Bleeker microscope with a 170 mm body tube and a 5× Huygenian eyepiece.

Objective ‘1’ shows a lot of astigmatism, its spherical correction and contrast are good.
Objective ‘3’ is of good quality, the field is quite flat and the contrast of the image is good.
Objective ‘7’ shows spherical overcorrection, the contrast of the image is not so well defined, however, the diatom Pleurosigma angulatum is still resolved into dots.

See also SM 68.