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Compound achromatic microscope, stand ‘Standart 14’

Maker

ZEISS

Country

Germany

Signature

Carl Zeiss / West Germany / 4761196

Category

Microscopes

Optical 1

Compound

Optical 2

Achromatic

Size of the microscope (h x b x d)

36.5 × 17 × 26 cm

Provenance

L. Smid, Delft

Inventory number

SM 15

Description

This is an injection-moulded, light grey-enamelled, aluminium stand. In the thick baseplate a built-in halogen lamp with its condenser and a prism directing the light upwards. At the bottom of the limb a block with the coarse and fine adjustment acting on the stage. The limb ends in a ring, below the quadruple objective changer and on top of the ring a bayonet mount for various eyepieces. This microscope has a binocular eyepiece. The microscope has a two-element condenser after Berek, the focal length of the total condenser is 12.95 mm. With low magnification objectives only the lower part of the condenser is used by folding away the upper part, the focal length of this part is 48.09 mm. The iris is located between the two elements in the focal plane of the upper part of the condenser. There is a holder for filters.
The microscope has a large mechanical stage.
The lamp is powered by a transformer made by Wild / Heerbrugg (h = 11.6 cm, w = 17.7 cm, d = 19 cm) from Swiss, there is a spare lamp.
With this microscope go two pairs of eyepieces, Kpl 8× and Kpl 12.5×, the 8× were added later and have not been measured yet.

Eyepiece 12.5×
Focal length (mm) 19.92
Magnification 12.55

The objectives that go with this microscope are all corrected for a 160 mm body tube, which is usual for Zeiss objectives.
Plan 2.5, NA 0.08, intended for use without cover glass, serial number 4384600.
Plan 25, NA 0.45, 0.17 mm cover glass (added later and not investigated yet).
Neofluar 10× / NA 0.30, intended for use without cover glass, serial number 4786904.
Neofluar 40×, NA 0.75, 0.17 mm cover glass, serial number 4823158. Damaged, probably by a fall.
Neofluar 63×, NA 0.90, with correction for cover glass 0.11-0.23 mm (added later and not investigated yet).
Neofluar 100×, NA1.30 Oel, serial number 4599836. The back lens is probably scratched.

The objectives were investigated using the Bleeker microscope, and a 160 mm body tube. The 2.5× and the 10× with a 10× Huygenian eyepiece, the 40× and 100× with a 5× Huygenian eyepiece.

Objective 2.5 10 40 100
Focal length (mm) 57.22 16.49 4.60 1.99
Magnification 25.58 98.40 201.72 492
Numerical aperture 0.085 0.31 0.79 1.33
Resolving power (µm) 4 1.3 < 0.8 < 0.8

Objective 2.5: star test okay.
Objective 10×: star test okay, the diffraction rings are a bit frayed, the diatom Navicula lyra is resolved into lines.
Objective 40×: some spherical overcorrection and a zonal defect. The diatom Pleurosigma angulatum is resolved into dots, Surirella gemma into lines.