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Compound achromatic microscope, stand III D

Year/Period	1921
Maker	ZEISS
Country	Germany
Signature	CARL ZEISS / JENA / Nr. 78244
Category	Microscopes
Optical 1	Compound
Optical 2	Achromatic
Size of the box (h x w x d)	38.1 × 21.5 × 21 cm
Size of the microscope (h x w x d)	32.5 × 13 × 15.5 cm
Inventory number	SM 36

Description

In mahogany box, the lock is lost.
Stand type III D, its nickname is ‘Bierseidel’ or Jug Handle, because of its characteristic grip. Zeiss introduced this stand in 1898, it was made until the nineteen twenties. A problem with the older large stands I and III was that it was usual to pick them up by their limb, the sensitive micrometer screw which was in the limb got damaged easily by this malpractice (these stands are very heavy, about 7 kilo). In the new Jug Handle this cannot happen so easily. Zeiss introduced a new fine adjustment as well, the Berger type micrometer screw, which acted on the block carrying the body tube and the coarse adjustment.
There were two main types, stand I with a large diameter body tube which was especially intended for micro-photography and stand III with a body tube of normal diameter. This stand III D has a plain circular stage, covered with ebonite, it can be centred and rotated. Below the stage an Abbe type condenser with an iris diaphragm that can be moved in and out of the optical axis and a flat and concave mirror in a bracket. There is a four-fold objective changer.
At a later date an attachable mechanical stage has been added, it is signed Zeiss/Winkel, serial number 128063.

With this microscope go the following eyepieces (the 20, 15 en 9 mm eyepieces are ‘Orthoscop’ eyepieces):

Eyepiece	1 (4×)	4 (10×)	20 mm	15 mm	9 mm
Focal length (mm)	63.95	25.08	20.61	14.89	9.34
Magnification	3.9	9.97	12.13	16.8	26.76

There are the following objectives:

Objective	A 3	A 8	AA	C	D	F
Serial number	13087	35406	17052	9516	28893	7324
Focal length (mm)	25.25	18.21	15.48	5.61	4.83	1.96
Magnification	5.1	8.1	10.42	20.25	39.5	98.8
Numerical aperture	0.083	0.21	0.33	0.41	0.64	0.96
Resolving power (µm)	4	1.6	1.3	1	0.48	0.41

Remarks:
A 3: star test good.
A 8: star test goed, flat field, very good contrast.
AA: star test good, flat field, good contrast. The diatom Navicula lyra is resolved into lines.
C: star test good. The diatom Navicula lyra is resolved into lines.
D: star test good. The diatom Pleurosigma angulatum is resolved into lines.
F: star test good. The diatom Surirella Gemma is resolved into lines.

Objective F is a special fluorite objective with a correction collar, this enables compensation of spherical aberration for different thicknesses of cover slips.

See also SM 33, stand III C and SM 413, stand I.